Astounding Stories of Super-Science, October, 1930, Page 2

  The Invisible Death

  A COMPLETE NOVELETTE

  _By Victor Rousseau_

  Far overhead a luminous shape appeared.]

  [Sidenote: With night-rays and darkness-antidote America strikes backat the terrific and destructive Invisible Empire.]

  CHAPTER I

  _Out of the Hangman's Hands_

  "You speak," said Von Kettler, jeering, "as if you really believedthat you had the power of life and death over me."

  The Superintendent of the penitentiary frowned, yet there wassomething of perplexity in the look he gave the prisoner. "VonKettler, I think it is time that you dropped this absurd pose ofyours," he said, "in view of the fact that you are scheduled to die byhanging at eight o'clock to-morrow night. Your life and death are inyour own hands."

  Von Kettler bowed ironically. Standing in the Superintendent'spresence in the uniform of the condemned cell, collarless,bare-headed, he yet seemed to dominate the other by a certain poise,breeding, nonchalance.

  "Your life is offered you in consideration of your making a completewritten confession of the whole ramifications of the plot against theFederal Government," the Superintendent continued.

  "Rather a confession of weakness, my dear Superintendent," jeered theprisoner.

  * * * * *

  "Oh don't worry about that! The Government has unravelled a good dealof the conspiracy. It knows that you and your international associatesare planning to strike at civilized government throughout the world,in the effort to restore the days of autocracy. It knows you areplanning a world federation of states, based on the principles ofabsolutism and aristocracy. It is aware of the immense financialresources behind the movement. Also that you have obtained the use ofcertain scientific discoveries which you believe will aid you in yourschemes."

  "I was wondering," jeered the prisoner, "how soon you were coming tothat."

  "They didn't help you in your murderous scheme," the Superintendentthundered. "You were found in the War Office by the night watchman,rifling a safe of valuable documents. You shot him with a pistolequipped with a silencer. You shot down two more who, hearing hiscries, rushed to his aid. And you attempted to stroll out of thebuilding, apparently under the belief that you possessed mysteriouspower which would afford you security."

  "A little lapse of judgment such as may happen with the best laidplans," smiled Von Kettler. "No, Superintendent, I'll be franker withyou than that. My capture was designed. It was decided to give theGovernment an object lesson in our power. It was resolved that Ishould permit myself to be captured, in order to demonstrate that youcannot hang me, that I have merely to open the door of my cell, thegates of this penitentiary, and walk out to freedom."

  "Have you quite finished?" rasped the Superintendent.

  "At your disposal," smiled the other.

  "Here's your last chance, Von Kettler. Your persistence in this absurdclaim has actually shaken the expressed conviction of some of themedical examiners that you are sane. If you will make that completewritten confession that the Government asks of you, I pledge you thatyou shall be declared insane to-night, and sent to a sanitarium fromwhich you will be permitted to escape as soon as this affair has blownover."

  * * * * *

  "The United States Government has sunk pretty low, to involve itselfin a deal of this character, don't you think, my dear Superintendent?"jeered Von Kettler.

  "The Government is prepared to act as it thinks best in the interestsof humanity. It knows that the death of one wretched murderer such asyourself is not worth the lives of thousands of innocent men!"

  "And there," smiled Von Kettler, without abating an atom of hisnonchalance, "there, my dear Superintendent, you hit the nail on thehead. Only, instead of thousands, you might have said millions."

  Von Kettler's aspect changed. Suddenly his eyes blazed, his voiceshook with excitement, his face was the face of a fanatic, of aprophet.

  "Yes, millions, Superintendent," he thundered. "It it a holy causethat inspires us. We know that it is our sacred mission to save theworld from the drabness of modern democracy. The people--always thepeople! Bah! what are the lives of these swarming millions worth whencompared with a Caesar, a Napoleon, an Alexander, a Charlemagne?Nothing can stop us or defeat us. And you, with your confession ofdefeat, your petty bargaining--I laugh at you!"

  "You'll laugh on the gallows to-morrow night!" the Superintendentshouted.

  Again Von Kettler was the calm, superior, arrogant prisoner of before."I shall never stand on the gallows trap, my dear Superintendent, as Ihave told you many times," he replied. "And, since we have reachedwhat diplomacy calls a deadlock, permit me to return to my cell."

  The Superintendent pressed a button on his desk; the guards, who hadbeen waiting outside the office, entered hastily. "Take this manback," he commanded, and Von Kettler, head held high, and smiling,left the room between them.

  * * * * *

  The Superintendent pressed another button, and his assistant entered,a rugged, red-haired man of forty--Anstruther, familiarly known as"Bull" Anstruther, the man who had in three weeks reduced thepenitentiary from a place of undisciplined chaos to a model of lawand order. Anstruther knew nothing of the Superintendent's offer toVon Kettler, but he knew that the latter had powerful friends outside.

  "Anstruther, I'm worried about Von Kettler," said the Superintendent."He actually laughed at me when I spoke of the possibility of anothermedical examination. He seemed confident that he could not be hanged.Swore that he will never stand on the gallows trap. How about yourprecautions for to-morrow night?"

  "We've taken all possible precautions," answered Anstruther. "Specialarmed guards have been posted at every entrance to the building.Detectives are patrolling all streets leading up to it. Every car thatpasses is being scrutinized, its plate numbers taken, and forwarded tothe Motor Bureau. There's no chance of even an attempt atrescue--literally none."

  "He's insane," said the Superintendent, with conviction, and the wordsfilled him with new confidence. It had been less Von Kettler'sstatements than the man's cool confidence and arrogant superioritythat had made him doubt. "But he's not too insane to have known whathe was doing. He'll hang."

  "He certainly will," replied Anstruther. "He's just a big bluff, sir."

  "Have him searched rigorously again to-morrow morning, and his celltoo--every inch of it, Anstruther. And don't relax an iota of yourprecautions. I'll be glad when it's all over."

  He proceeded to hold a long-distance conversation with Washington overa special wire.

  * * * * *

  In his cell, Von Kettler could be seen reading a book. It wasNietzsche's "Thus Spake Zarathusta," that compendium of aristocraticinsolence that once took the world by storm, until the author'smentality was revealed by his commitment to a mad-house. Von Kettlerread till midnight, closely observed by the guard at the trap, thenlaid the word aside with a yawn, lay down on his cot, and appeared tofall instantly asleep.

  Dawn broke. Von Kettler rose, breakfasted, smoked the perfecto thatcame with his ham and eggs, resumed his book. At ten o'clock BullAnstruther came with a guard and stripped him to the skin, examiningevery inch of his prison garments. The bedding followed; the cell wasgone over microscopically. Von Kettler, permitted to dress again,smiled ironically. That smile stirred Anstruther's gall.

  "We know you're just a big bluff, Von Kettler," snarled the big man."Don't think you've got us going. We're just taking the usualprecautions, that's all."

  "So unnecessary," smiled Von Kettler. "To-night I shall dine at theAmbassador grill. Watch for me there. I'll leave a memento."

  Anstruther went out, choking. Early in the afternoon two guards camefor Von Kettler.

  "Your sister's come to say good-by to you," he was told, as he wastaken to the visitors' cell.

  This was a large and fairly comfortable cell in a corridor leading offthe death house
, designed to impress visitors with the belief that itwas the condemned man's permanent abode; and, by a sort of convention,it was understood that prisoners were not to disabuse their visitors'minds of the idea. The convention had been honorably kept. Thevisitor's approach was checked by a grill, with a two-yards spacebetween it and the bars of the cell. Within this space a guard wasseated: it was his duty to see that nothing passed.

  * * * * *

  As soon as Von Kettler had been temporarily established in his newquarters, a pretty, fair-haired young woman came along the corridor,conducted by the Superintendent himself. She walked with dignity, herbearing was proud, she smiled at her brother through the grill, andthere was no trace of weeping about her eyes.

  She bowed with pretty formality, and Von Kettler saluted her with anairy wave of the hand. Then they began to speak, and the German guardwho had been selected for the purpose of interpreting to theSuperintendent afterward, was baffled.

  It was not German--neither was it French, Italian, or any of theRomance languages. As a matter of fact, it was Hungarian.

  Not until the half-hour was up did they lapse into English, and allthe while they might have been conversing on art, literature, orsport. There was no hint of tragedy in this last meeting.

  "Good-by, Rudy," smiled his sister, "I'll see you soon."

  "To-night or to-morrow," replied Von Kettler indifferently.

  The girl blew him a kiss. She seemed to detach it from her mouth andextend it through the grill with a graceful gesture of the hand, andVon Kettler caught it with a romantic wave of the fingers and strainedit to his heart. But it was only one of those queer foreign ways.Nothing was passed. The alert guard, sitting under the electric light,was sure of that.

  They searched Von Kettler again after he was back in the death house.The other cells were empty. In three of them detectives were placed.In the yard beyond the hangman was experimenting with the trap. Hehimself was under close observation. Nothing was being left to chance.

  * * * * *

  At seven o'clock two men collided in the death-house entrance. One wasa guard, carrying Von Kettler's last meal on a tray. He had demandedPerigord truffles and pate de foie gras, cold lobster, endive salad,and near-beer, and he had got them. The other was the chaplain, in astate of visible agitation.

  "If he was an atheist and mocked at me it wouldn't be so bad," thegood man declared. "I've had plenty of that kind. But he says he's notgoing to be hanged. He's mad, mad as a March hare. The Government hasno right to send an insane man to the gallows."

  "All bluff, my dear Mr. Wright," answered the Superintendent, when thechaplain voiced his protest. "He thinks he can get away with it. Thecommission has pronounced him sane, and he must pay the penalty of hiscrime."

  By that mysterious process of telegraphy that exists in all penalinstitutions, Von Kettler's boast that he would beat the hangman hadbecome the common information of the inmates. Bets were being laid,and the odds against Von Kettler ranged from ten to fifteen to one. Itwas generally agreed, however, that Von Kettler would die game to thelast.

  "You all ready, Mr. Squires?" the prowling Superintendent asked thehangman.

  "Everything's O. K., sir."

  The Superintendent glanced at the group of newspaper men gatheredabout the gallows. They, too, had heard of the prisoner's boast. Oneof them asked him a question. He silenced him with an angry look.

  "The prisoner is in his cell, and will be led out in ten minutes. Youshall see for yourselves how much truth there it in this absurdity,"he said.

  * * * * *

  He looked at his watch. It lacked five minutes of eight. Thepreparations for an execution had been reduced almost to a formula.One minute in the cell, twenty seconds to the trap, forty seconds forthe hangman to complete his arrangements: two minutes, and then thethud of the false floor.

  Four minutes of eight. The little group had fallen silent. The hangmanfurtively took a drink from his hip-pocket flask. Three minutes! TheSuperintendent walked back to the door of the death house and noddedto the guard.

  "Bring him out quick!" he said.

  The guard shot the bolt of Von Kettler's cell. The Superintendent sawhim enter, heard a loud exclamation, and hurried to his side. Oneglance told him that the prisoner had made good his boast.

  Von Kettler's cell was empty!

  CHAPTER II

  _Conference_

  Captain Richard Rennell, of the U. S. Air Service, but temporarilydetached to Intelligence, thought that Fredegonde Valmy had neverlooked so lovely as when he helped her out of the cockpit.

  Her dark hair fell in disorder over her flushed cheeks, and her eyeswere sparkling with pleasure.

  "A thousand thanks, M'sieur Rennell," she said, in her low voice withits slight foreign intonation. "Never have I enjoyed a ride more thanto-day. And I shall see you at Mrs. Wansleigh's ball to-night?"

  "I hope so--if I'm not wanted at Headquarters," answered Dick, lookingat the girl in undisguised admiration.

  "Ah, that Headquarters of yours! It claims so much of your time!" shepouted. "But these are times when the Intelligence Service demandsmuch of its men, is it not so?"

  "Who told you I was attached to Intelligence?" demanded Dick bluntly.

  She laughed mockingly. "Do you think that is not known all overWashington?" she asked. "It is strange that Intelligence should actlike the--the ostrich, who buries his head in the sand and thinks thatno one sees him because it is hidden."

  Dick looked at the girl in perplexity. During the past month he hadcompletely lost his head and heart over her, and he was trying to viewher with the dispassionate judgment that his position demanded.

  As the niece of the Slovakian Ambassador, Mademoiselle Valmy had theentry to Washington society. The Ambassador was away on leave, and shehad appeared during his absence, but she had been acceptedunquestionably at the Embassy, where she had taken up her quarters,explaining--as the Ambassador confirmed by cable--that she had sailedunder a misconception as to the date of his leave.

  * * * * *

  Brunette, beautiful, charming, she had a score of hearts to play with,and yet Dick flattered himself that he stood first. Perhaps the othersdid too.

  "Of course," the girl went on, "with the Invisible Emperor threateningorganized society, you gentlemen find yourselves extremely busy. Well,let us hope that you locate him and bring him to book."

  "Sometimes," said Dick slowly, "I almost think that you know somethingabout the Invisible Emperor."

  Again she laughed merrily. "Now, if you had said that my sympathieswere with the Invisible Emperor, I might have been surprised into anacknowledgment," she answered. "After all, he does stand for thataristocracy that has disappeared from the modern world, does he not?For refinement of manners, for beauty of life, for all those thingsmen used to prize."

  "Likewise for the existence of the vast body of the nation inignorance and poverty, in filth and squalor," answered Dick. "No, mysympathies are with law and order and democracy, and your InvisibleEmperor and his crowd are simply a gang of thieves and hold-up men."

  "Be careful!" A warning fire burned in the girl's eyes. "At least, itis known that the Emperor's ears are long."

  "So are a jackass's," retorted Dick.

  He was sorry next moment, for the girl received his answer in icysilence. In his car, which conveyed them from the tarmac to theEmbassy, she received all his overtures in the same silence. A frigidlittle bow was her farewell to him, while Dick, struggling betweenresentment and humiliation, sat dumb and wretched at the wheel.

  Yet the idea that Fredegonde Valmy had any knowledge of the conspiracyor its leaders never entered Dick's head. He was only miserable thathe had offended her, and he would have done anything to havestraightened out the trouble.

  * * * * *

  It seemed impossible that in the year 1940 the peace of the civilizedwo
rld could be threatened by an international conspiracy bent onrestoring absolutism, and yet each day showed more clearly the immenseramifications of the plot. Each day, too, brought home to theinvestigating governments more clearly the fact that the things theyhad discovered were few in number in comparison with those they hadnot.

  The headquarters of the conspirators had never been discovered, and itwas suspected that the powerful mind behind them was intentionallyleading the investigators along false trails.

  The conspiracy was world-wide. It had been behind the revolution thathad recreated an absolutist monarchy in Spain. It had plunged Italyinto civil war. It had thrown England into the convulsions of asuccession of general strikes, using the communist movement as a cloakfor its activities.

  But nobody dreamed that America could become a fertile field for itsinsidious propaganda. Yet it was behind the millions of adherents ofthe so-called Freemen's Party, clamoring for the destruction of theconstitution. Upon the anarchy that would follow the absolutist regimewas to be erected.

  Already the mysterious powers had struck. Departments of State hadbeen entered and important papers abstracted. The _Germania_ hadmysteriously disappeared in mid-Atlantic, and a shipping panic hadensued. There were tales of mysterious figures materializing out ofnothingness. It was known that the conspirators were in possession ofcertain chemical and electrical devices with which they hoped toachieve their ends.

  The Superintendent of the penitentiary had had in his pocket anauthorization to stop the execution of Von Kettler after he stood onthe trap. Dead, he would be a mere mark of vengeance: alive, he mightbe persuaded to furnish some clue to the headquarters of themiscreants.

  * * * * *

  And behind the conspirators loomed the unknown figure that signeditself the Invisible Emperor--in the communications that poured in tothe White House and to the rulers of other nations. In the threatsthat were materializing with stunning swiftness.

  Who was he? Rumor said that a former European ruler had not died aswas supposed: that a coffin weighted with lead had been buried, andthat he himself in his old age, had gone forth to a mad scheme ofworld conquest with a body of his nobles.

  It had been practically a state of war since the shipment of gold,guarded by a detachment of police, had been stolen in broad daylightoutside Baltimore, the police clubbed and killed by invisibleassailants--as they claimed. The press was under censorship, troopsunder arms, and it was reported that the fleet was mobilizing.

  In the midst of it all, Washington shopped, danced, feasted, flirted,like a swarm of may flies over a treacherous stream.

  Intelligence was alert. As Dick started to drive away from theSlovakian Embassy, a man stepped quickly to the side of the car andthrust an envelope into his hand. Dick opened it quickly. He waswanted by Colonel Stopford at once, not at the camouflagedHeadquarters at the War Department, but at the real Headquarters whereno papers were kept but weighty decisions were made. And to thatdevious course the Government had already been driven.

  Dick parked his car in a side street--it would have been underespionage in any of the official parking places--and set off at asmart walk toward his destination. Nobody would have guessed, from theappearance of the streets, that a national calamity was impending. Theshopping crowds were swarming along the sidewalks, cars tailed eachother through the streets; only a detachment of soldiers on the WhiteHouse lawn lent a touch of the martial to the scene.

  * * * * *

  The building which Dick entered was an ordinary ten-story one in thebusiness section; the various legal firms and commercial concerns thatoccupied it would have been greatly surprised to have known theidentity of the Ira T. Graves, Importer, whose name appeared in modestletters upon the opaque glass door on the seventh story. Inside aflapper stenographer--actually one of the most trusted members ofIntelligence's staff--asked Dick's name, which she knew perfectlywell. Not a smile or a flicker of an eyelid betrayed the fact.

  "Mr. Rennell," said Dick with equal gravity.

  The girl passed into an inner room, and a buzzer sounded. In a fewmoments the girl came back.

  "Mr. Graves will be here in a few minutes, Mr. Rennell, if you'llkindly wait in his office," she said.

  Dick thanked her, and walked through into the empty office. He waitedthere till the girl had closed the door behind him, then went out byanother door and found himself again in the corridor. Opposite him wasa door with the words "Entrance 769" and a hand pointing down thecorridor to where the Intelligence service had established anotherperfectly innocent front. Dick tapped lightly at this door, and a keyturned in the lock.

  The man who stepped quickly back was one of the heads of the CivilService. The man at the flat-topped desk was Colonel Stopford. The manon a chair beside him was one of the heads of the police force.

  * * * * *

  The Colonel, a big, elderly man, dressed in a grey sack suit, checkedDick's commencing salutation. "Never mind etiquette, Rennell," hesaid. "Sit down. You've heard about the man Von Kettler's escape lastnight, of course?"

  "Yes, sir."

  "It's known, then. We can't keep things dark. He vanished from hiscell in the death house, three minutes before the time appointed forhis execution, though, as a matter of fact, he wasn't going to behanged. Apparently he walked through the walls.

  "There's a sequel to it, Rennell. It seems he had told theassistant-superintendent, a man named Anstruther, that he'd meet himat a restaurant in town that night. He promised to leave him amemento. Anstruther happened to remember this boast of Von Kettler's,and he surrounded the restaurant with armed detectives, on the chancethat the fellow would show up. Rennell, _Von Kettler was there!_"

  "He went to this restaurant, sir?"

  "He walked in, just before the place was surrounded, engaged a table,and ordered a sumptuous meal. He told the waiter his name, said heexpected a friend to join him, walked into the wash-room--andvanished! Two minutes later Anstruther and his men were on the job.Von Kettler never came out of the wash-room, so far as anybody knows.

  "In the midst of the hue and cry somebody pointed to the table thatVon Kettler had engaged. There was a twenty-dollar bill upon it, and ascrap of paper reading: 'I've kept my word. Von K.'"

  Colonel Stopford looked at Dick fixedly. "Rennell, we may be fools,"he said, "but we realize what we're up against. It's a big thing, andwe're going to need all our fighting grit to overcome it. You're oneof the four men we're depending on. We're counting on you because ofyour record, and because of your degree in science at Heidelberg. ThePresident wishes you to take charge of the whole Eastern IntelligenceDistrict, covering the entire south-eastern seaboard of the UnitedStates. You are to have complete freedom of action, and all civil,military, and naval officials have received instructions to co-operatewith you."

  "There goes Mrs. Wansleigh's ball," thought Dick, but he said nothing.

  * * * * *

  "We're not the hunters, Dick Rennell," went on Colonel Stopford."We're hiding under cover, and I'm counting on you to turn the tables.They even know my office is here. I had a long distance call fromSavannah this morning in mocking vein. They advised me to have theWhite House watched to-night. I warned the President, and we've postedguards all round it."

  "They held the wire while you called up the President?" asked Dick.

  "Damn it, no! They called me up from Scranton the instant he'dfinished speaking. They have the power of the devil, Rennell, withthat infernal invisibility invention of theirs. Rennell, we'refighting unknown forces. Who this Invisible Emperor is, we don't evenknow. But one thing we've found out. He has his headquarters somewherein your district. Somewhere along the south Atlantic seaboard. Thegreater part of his activities emanate from there. But we're fightingin the dark. The clue, the master clue that will enable us to locatehim--that's what we lack."

  The sun had set, it was beginning to grow dark. Colonel Stopfords
witched on the electric lamp beside his desk.

  "What have you to say, Rennell?" he asked; and Dick was aware that thetwo other men were regarding him attentively.

  "It's evident," said Dick, "that Von Kettler possessed this means ofinvisibility in his cell, and wasn't detected. He simply slipped outwhen the guard came to fetch him."

  "Invisibility? Yes! But invisible's not the same thing astransparent," cried Stopford. "These folks have operated in broaddaylight. They're transparent, damn them! Not even a shadow! You knowwhat I mean, Rennell! What I'm thinking of! That crazy man you were intouch with six months ago, who prophesied this! We turned him down! Heshowed me a watch and said the salvation of the world was inside thecase! I thought him insane!"

  * * * * *

  "You mean Luke Evans, sir. That watch was his pocket model. He wentoff in a huff, saying the time would come when we'd want him and notbe able to find him."

  "But, damn him, he wanted to produce universal darkness, or some suchnonsense, Rennell, and I told him that we wanted light, not darkness."

  "It wasn't exactly that, sir." Colonel Stopford was a man of the oldschool: he had been an artillery officer in the Great War, and wascharacteristically impatient of new notions. Dick began carefully:"You'll remember, sir, old Evans claimed to have been the inventor ofthat shadow-breaking device that was stolen from him and sold inEngland."

  "To a moving picture company!" snorted Stopford. "I asked him whatmoving pictures had to do with war."

  "Evans was convinced that the invention would be applied to war. Heclaimed that it made the modern methods of military camouflage out ofdate completely. He said that by destroying shadows one could produceinvisibility, since visibility consists in the refraction of wavelengths by material objects.

  "When they stole his invention, he foresaw that it would be used inwar. He set to work to nullify his own invention. He told me that hehad unintentionally given to the enemies of the United States a meansof bringing us to our knees, since he believed that British motionpicture company was actually a subsidiary of Krupp's. He worked out amethod of counteracting it."

  "You must get him, Rennell. Even if it's all nonsense, we can't affordto let any chance go. If Evans's invention will counteract this damnedinvisibility business--"

  The telephone on the Colonel's desk rang. He picked it up, and hisface assumed an expression of incredulity. He looked about him, like aman bewildered. He beckoned to the police official, who hurried to hisside, and thrust the receiver into his hand. The official listened.

  "All right," he said. He turned to Dick and the Civil Servicerepresentative.

  "Gentlemen," he said, "the President has disappeared from his officein the White House, and there are grave fears that he has beenkidnapped!"

  CHAPTER III

  _In the White House_

  Colonel Stopford's car had been parked around the corner of thebuilding, and within a minute the four men were inside it, Stopford atthe wheel, and racing in the direction of the White House. A nod tothe guard at the gate, and they were inside the grounds. At theentrance a single guard, in place of the four who should have beenposted there, challenged sharply, and attempted to bar the way, notrecognizing Dick or Stopford in their civilian clothes.

  "Where's your officer?" demanded Stopford sharply.

  Half-cowed by the Colonel's manner, the young recruit hesitated, andthe four swept him out of the way and hurried on. The scene outsidethe main entrance to the White House was one of indescribableconfusion. Soldiers were swarming in confused groups, some trying toforce an entrance, others pouring out. Every moment civilians,streaming over the lawn, added to the number. Discipline seemed almostabandoned. From inside the building came outbursts of screams andcursing, the scuffling of a mob.

  "Roscoe! Roscoe!" shouted Stopford. "Where's the President'ssecretary? Who's seen him? Let us pass immediately!"

  No one paid the least attention to him. But a short, bare-headedcivilian, who was struggling in the crowd, heard, and shouted inanswer, waved his arms, and began to force his way toward the four. Itwas Roscoe, the secretary of President Hargreaves. The President was achildless widower, and Roscoe lived in the White House with him andwas intimately in his confidence.

  Roscoe gained Stopford's side. "Say--they've got him!" he panted."They've got him somewhere--inside the building. They're trying to gethim out! We've got to save him--but we can't see them--or him. They'vemade him invisible too, curse them! I heard him crying, 'Help me,Roscoe!' He saw me, I tell you--and I didn't know where he was!"

  * * * * *

  The little secretary was almost incoherent with fear and anger. Thefive men, forming a wedge, hurled themselves forward. Out of the WhiteHouse entrance appeared a tall officer, revolver in hand. It wasColonel Simpson, of the President's staff. Half beside himself, heswept the weapon menacingly about him, shouting incoherently, andclearing a passage, into which the five hurled themselves.

  Stopford seized his revolver hand, and after a brief struggle Simpsonrecognized him.

  "He's in the building!" he shouted wildly. "Somewhere upstairs! I'mtrying to form a cordon, but this damned mob's in the way. Kick thosecivilians out!" he cried to the soldiers. "Shoot them if they don'tgo! Guard the windows!"

  Stopford and Dick, at the head of the wedge, pushed past into theWhite House. The interior was packed, men were struggling franticallyon the staircase; it seemed hopeless to try to do anything.

  Suddenly renewed yells sounded from above, a scream of anguish, howlsof terror. There came a downward surge, then a forward and upward one,which carried the two men up the stairs and into the President'sprivate apartments above.

  In the large reception-room a mob was struggling at a window, beneatha blaze of electric light. A soldier was standing there like a statue,his face fixed with a leer of horror. In his hands was a rifle, with ablood-stained bayonet, dripping upon the hardwood floor at the edge ofthe rug. Upon the rug itself a stream of blood was spouting out of theair.

  Dick looked at the sight and choked. There was something appalling inthe sight: it was the quintessence of horror, that widening pool ofblood, staining the rug, and flowing from an invisible body thatwrithed and twisted, while moans of anguish came from unseen lips.

  Colonel Stopford leaped back, livid and staring. "God, it's goteyes--two eyes!" he shouted.

  Dick saw them too. The eyes, which alone were visible, were about sixinches from the floor, and they were appearing and disappearing, asthey opened and shut alternately. It was a man lying there, a dyingman, pierced by the soldier's bayonet by pure accident, dying and yetinvisible.

  * * * * *

  The mob had scattered with shrieks of terror, but a few bolder spiritsremained in a thin circle about that fearful thing on the rug. Dickbent over the man, and felt the outlines of the writhing body. It wasa man, apparently dressed in some sort of uniform, but this wascovered, from the top of the head to the feet, with a sort of sheersilken garment, bifurcating below the waist, and resembling a cocoon.It seemed to appear and alternately to vanish.

  Dick seized the filmy stuff in his fingers, rent it, and stripped itaway. Yells of terror and amazement broke from the throats of all.Instantly the thin circle of spectators had become reinforced by astruggling mass of men.

  The half-visible cocoon clung to Dick's body like spider webs. But theman who had been wearing it had sprung instantly into view beneath thecluster of electric lights. He was a fair-haired young fellow of aboutthirty years, his features white and set in the agony of death.

  He was dressed in a trim uniform of black, with silver braid, and onhis shoulders were the insignia of a lieutenant. He opened his eyes,blue as the skies, and stared about him. He seemed to understand whathad happened to him.

  "Dogs!" he muttered.

  Shrieks of fury answered him. The mob surged toward him as if to grindhis face to pieces under their feet--and then recoiled, mouthing andgib
bering. But it was at Dick that they were looking, not at the dyingman.

  He raised himself upon one elbow with a mighty effort. "His Majestythe Invisible Emperor! Long be his reign triumphant!" he chanted. Itwas his last credo. The words broke from his lips accompanied by atorrent of red foam. His head dropped back, his body slipped down; hewas gone. And no one seemed to observe his passing. They were allscreaming and gibbering at Dick.

  "Rennell! Rennell!" yelled Stopford. "Where are you, Rennell? God,man, what's happened to your legs?"

  Dick looked down at himself. For a moment he had the illusion that hewas a head and a trunk, floating in the air. His lower limbs hadbecome invisible, except for patches of trousering that seemed todrift through space. The mob in the room had fallen back gaping at himin horror.

  Then Dick understood. It was the invisible garment that had coileditself about him. He tore it from him and became visibly a man oncemore.

  Shouts from another room! A surging movement of the crowd toward it.The muffled sounds of an automatic pistol, fitted with a silencer!Then screams:

  "The devils are in there! They're murdering the soldiers!"

  There followed a panic-stricken rush, more muffled firing, and thenthe sharp roar of rifles, and the fall of plaster. Some one wasbawling the President's name. The rooms became a mass of milling humanbeings, lost to all self-control.

  A bedlam of noise and struggle. Men fought with one another blindly,cursing soldiers fired promiscuously among the mob, riddling thewalls, stabbing at the air. The plaster was falling in great chunkseverywhere, filling the rooms with a heavy white cloud, in which allchoked and struggled. The yells of the civilian mob below, strugglinghelplessly in the packed crowd that wedged the great stairway, madebabel. Outside the White House a dense mob that filled the lawns wasyelling back, and struggling to gain admittance. Suddenly the lightswent out.

  "They've cut the wires!" rose a wild, wailing voice. "The devils havecut the wires! Kill them! Kill everybody!"

  His cry ended in a gurgle. Somewhere in that dark hell a struggle wasgoing on, a well defined struggle, different from the random, aimlessbattling of the half-crazed soldiers and the civilians. PresidentHargreaves was still within the walls of the White House, it wasknown; it was physically impossible for him to have been carried awaywhen every foot of space was packed. And through that darkness theinvisible assailants were edging him, foot by foot, toward theoutside.

  * * * * *

  Dick was on the edge of this silent battle. He sensed it. Bracinghimself against a bureau, while the mob surged past him, he tried topierce the gloom, to reinforce with his perceptions what his instincttold him. A soldier, crazed with fear, came leaping at him, bayonetleveled. He thrust with a grunt. Dick avoided the glancing steel by ahand's breadth, and, as the impetus of the man's attack carried himforward, caught him beneath the chin with a stiff right-hand jolt thatsent him sprawling.

  From below the cries broke out again, with renewed violence: "They'vegot the President! Get them! Get them! Close all doors and windows!"

  But a door went crashing down somewhere, to the tune of savage yells.The mob was pouring down the stairs. It was growing less packed above.Dick heard Stopford's voice calling his name.

  "Here, sir" he shouted back, and the two men collided.

  "For God's sake do what you can, Rennell!" shouted the Colonel."They've got the President downstairs. They had him in this very room,in the thick of it all. I heard him cry out, as if under a gag. Theyput one of those damned cloths over him. God, Rennell, I'm goingcrazy!"

  The upper floor of the White House was almost empty now. Dick thrusthimself into the crowd that still jammed the stairs. He reached theground floor. It was lighter here, but a glance showed him that it wasimpossible to attempt to restore any semblance of order. The big EastRoom was jammed with a fighting, cursing throng. Dick stumbled overthe bodies of those who had fallen in the press, or had been shotdown. Outside the mob was thickening, swarming through the grounds andscreeching like madmen.

  * * * * *

  Nothing that could be done! Dick found himself caught once more in thehuman torrent. Presently he was wedged up against a broken window. Heprecipitated himself through the frame, dropped to the ground, stoppedfor an instant to catch breath.

  The yelling mob was congregated about the main entrance of the WhiteHouse, and on this side the grounds were comparatively empty. As Dickstopped, trying desperately to form some plan of action, he heardfootsteps and low voices near him. Then two men came toward him,followed by three or four others.

  The men--but, though the light was faint, Dick realized instantly thatthey were wearing invisible garments. He could see nothing of them; hecould see through where they seemed to be--the trees, the buildings ofthe streets. Yet they were at his elbow. And they saw him. He heardone of them leap, and sprang aside as the butt of a pistol descendedthrough the air and dropped where his head had been.

  Yet no hand had seemed to hold it. It had been a pistol, reversed, andflashing downward, to be arrested in mid-air six inches from his face.But the men were not wholly invisible. Nearly six feet above theground, three or four pairs of eyes were staring malevolently intoDick's. Only the eyes were there.

  The two foremost men were breathing heavily. They were carryingsomething. Grotesquely through a rent in the invisible garment Dicksaw a patch of trouser. He heard a muffled sigh. President Hargreaves,in the hands of his abductors!

  Dick's actions were reflex. As the pistol hung beside his face, hesnatched at it, wrested it away, struck with it, and heard a curse andfelt the yielding impact of bone and flesh. He had missed the head butstruck the shoulder. Next moment hands gripped the weapon, and adesperate struggle began.

  * * * * *

  It was torn from Dick's grasp. He struck out at random, and his fistcollided with the chin of a substantial flesh and blood human being.Invisible arms grasped him. He fought free. The pistol slashed hisface sidewise, the sight ripping a strip of flesh from the cheek. Hewas surrounded, he was being beaten down, though he was fightinggamely.

  "Kill the swine! Shoot! Shoot!" Dick heard one of his assailantsmuttering.

  Out of the void appeared the blue muzzle of another automatic, with asilencer on it. Dick ducked as a flame spurted from it. He felt thebullet stir his hair. He grasped at the hand that held it, and missed.Then he was held fast, and the muzzle swung implacably toward his headagain. Helpless, he watched it describe that arc of death. It was onlylater that he wondered why he had fought all the while in silence,instead of crying for help.

  But of a sudden the pistol was dashed aside. A woman's voice spokeperemptorily, in some language Dick did not understand. And he saw hereyes among the eyes that glared at him. Dark eyes that he knew, evenif the voice had not revealed her identity. The eyes and voice ofFredegonde Valmy!

  Dick cried her name. He put forth all his strength in a finalstruggle. Suddenly he felt a stunning impact on the back of the head.He slipped, reeled, threw out his hands, and sank down unconscious onthe grass at the side of the path.

  CHAPTER IV

  _The Invisible Ambassador_

  Fredegonde Valmy implicated in the conspiracy! That was the firstthought that flashed into Dick's mind as he recovered consciousness.He might have suspected it! But the idea that the girl he loved wasbound up with the murderous gang that was attacking the veryfoundations of civilization chilled him to the soul.

  Dick had been picked up a few minutes after he had been struck down,identified by Colonel Stopford as he was about to be removed to ahospital, and carried into the White House. Order had been restored bythe arrival of a detachment of troops from Fort Myers, the severedcables located and mended, and by midnight the interior of thePresidential home had been made habitable again.

  President Hargreaves was gone--kidnapped despite the utmost efforts toprotect him; and it was impossible to conceal that fact from theworld. But the whe
els of government still revolved. All night anemergency council sat in the White House, and, deciding that in a timeof such grave danger heroic means must be adopted, with the consent ofsuch of the Congressional leaders as could be summoned, a Council ofDefence was organized.

  The whole country east of the Mississippi was placed under martiallaw. The fleet and army were put on a war footing. Flights ofairplanes were assembled at numerous points along the easternseaboard. To this Council Donald was attached as head of Intelligencefor the Eastern Division. Yet all this availed little unless thelocation of the Invisible Empire could be ascertained, and, despitetelegraphic reports that came in hourly, alleging to have discoveredits headquarters, nothing had been achieved in this direction.

  * * * * *

  The garment taken from the slain soldier had been examined by ahalf-dozen of the leading chemists of the East. Pending the arrivalfrom New York of the celebrated Professor Hosmeyer, it was depositedunder military guard in a dark closet. The result was unfortunate. Thegarment exhibited to the assembled scientists was a mere bifurcatedsilken bag.

  The gas with which it had been impregnated, though it had been heavyenough to adhere to the fabric for hours, had also been volatileenough to have disappeared completely, leaving a residue which wasidentified as a magnesium isotope.

  Equally spectacular had been the disappearance of MademoiselleFredegonde Valmy. A cable from the Slovakian Ambassador had arrived afew hours later, denying her authenticity. And with her disappearancecame the discovery that she had been at the head of an espionagesystem with ramifications in every state department, and in everystatesman's home.

  Three days passed with no sign from the enemy. The Council sat allday. In the executive offices of the White House Dick toiledceaselessly, planning, receiving reports, organizing the flights ofairplanes at strategic points throughout his district. From time totime he would be summoned to the Council. At night he threw himselfupon a cot in his office and slept a sleep broken by the constantarrival of messengers. And still there was no clue to the location ofthe headquarters of the marauders.

  But in those three days there had been no sign of them. Hope hadsucceeded despair; in the rebound of confidence the populace wasbeginning to ridicule the nation-wide precautions against what werecoming to be considered merely a gang of super-criminals. It was evenwhispered that President Hargreaves had not been kidnapped at all. TheFreemen's Party accused the Government of a plot to subvert popularliberties.

  * * * * *

  Dick received a summons on the third evening. Utterly worn out withhis work, he pulled himself together and made his way into the BlueRoom, where the Council was assembled. Vice-president Tomlinson, anelderly man, was in the chair. A non-entity, pushed into a post it hadbeen thought he would adorn innocuously, he had been overwhelmed byhis succession to the chief office of State.

  Tomlinson did not like Dick, or any of the hustling younger officerswho, unlike himself, realized the real significance of the danger thatoverhung the country. He sat pompously in his leather chair, regardingDick as he entered in obedience to the summons.

  "Well, Captain Rennell, what have you to report to us this evening?"he inquired, as Dick saluted and stood to attention at the table.

  "We're improving our concentrations, Mr. Vice-president. We've eightflights of seaplanes scouring the coast in the hope of locating thestronghold of the Invisible Emperor. We've--"

  "I'm sick and tired of that title," shouted Tomlinson. He sprang tohis feet, his face flushed with anger. His nerves had broken under thecontinuous strain. "I'll give you my opinion, Captain Rennell," hesaid. "And that is that this so-called Invisible Emperor is a myth.

  "A gang of thieves has invented a paint that renders theminconspicuous, has created a panic, and is taking advantage of it toterrorize the country. The whole business is poppycock, in my opinion,and the sooner this bubble bursts the better. Well, sir, what have youto say to that?"

  "Have you ever seen any of these men in their invisible clothing, if Imay ask, Mr. Vice-president?" inquired Dick, trying to keep down hisanger. His nerves, too, were badly frazzled.

  "No, sir, I have not, but my opinion is that this story is grosslyexaggerated, and that the persons responsible are the reporters of oursensational press!" thundered Tomlinson.

  * * * * *

  He looked about him, a weak man proud of having asserted hisauthority. Somebody laughed.

  Tomlinson glared at Dick, his rubicund visage purpling. But it was notDick who had laughed. Nor any one at the council table.

  That laugh had come from the wall beside the door. Again it brokeforth, high-pitched, cold, derisive. All heads turned as if uponpivots to see who had uttered it.

  "Good God!" exclaimed Secretary Norris, of the War Department, andslumped in his chair.

  Five feet eight inches from the floor a pair of grey eyes looked atthe Council members out of emptiness. Grey eyes, a man's eyes, cool,contemptuous, and filled with authority, with a contemptuous sense ofsuperiority that left every man there dumb.

  Dick was the first to recover himself. He stepped forward, not towhere the invisible man was standing, but to a point between him andthe door.

  That cold laugh broke forth again. "Gentlemen, I am an ambassador frommy sovereign, who chooses to be known as the Invisible Emperor," camethe words. "As such, I claim immunity. Not that I greatly care, shouldyou wish to violate the laws of nations and put me to death. But,believe me, in such case the retribution will be a terrible one."

  Suddenly the envoy peeled off the gas-impregnated garments thatcovered him. He stood before the Council, a fair-haired young man,clad in the same fashion of trim black uniform as the bayonettedsoldier had worn upstairs three nights before.

  He bowed disdainfully, and it was Tomlinson who shouted:

  "Arrest that man! I know his face! I've seen it in the papers. He'sVon Kettler, the murderer who escaped from jail in an invisible suit."

  "Oh, come, Mr. Vice-president," laughed Von Kettler, "are you surethis isn't all very much exaggerated?"

  Tomlinson sank back in his chair, his ruddy face covered with sweat.Dick stared at Von Kettler. A suspicion was forming in his mind. Hehad seen eyes like those before, dark instead of grey, and yet withthe same look of pride and breeding in them; the look of the face,too, impossible to mistake--he knew!

  Fredegonde Valmy was Von Kettler's sister!

  * * * * *

  "Well, gentlemen, am I to receive the courtesies of an ambassador?"inquired Van Kettler, advancing.

  "You shall have the privileges of the gallows rope!" shoutedTomlinson. "Arrest that man at once, Captain Rennell!"

  "Pardon me, Mr. Vice-president," suggested the Secretary for the Navyblandly, "but perhaps it would be more desirable to hear what he hasto say."

  "Immunity for thieves, robbers, murderers!"

  "Might I suggest," said Von Kettler suavely, "that, since the UnitedStates has honored my master by placing itself upon a war footing, ithas accorded him the rights of a belligerent?"

  "We'll hear you, Mr. Von Kettler," said the Secretary of State,glancing along the table. Three or four nodded, two shook their heads:Tomlinson only glared speechlessly at the intruder. Von Kettleradvanced to the table and laid a paper upon it.

  "You recognize that signature, gentlemen?" he asked.

  At the bottom of the paper Dick saw scrawled the bold and unmistakablesignature of President Hargreaves.

  "An order signed by the President of your country," purred VonKettler, "ordering your military forces replaced upon a peace footing,and the acceptance of our conditions. They are not onerous, and willnot interfere with the daily life of the country. Merely a littlechange in that outworn document, the Constitution. My master rulesAmerica henceforward."

  Somebody laughed: another laughed: but it was the Secretary of Statewho did the fine thing. He took up the paper bearing what pur
ported tobe President Hargreaves's signature, and tore it in two.

  "The people of this country are her rulers," he said, "not an old mandragooned into signing a proclamation while in captivity--if indeedthat is President Hargreaves's signature."

  * * * * *

  There came a sudden burst of applause. Von Kettler's face became themask of a savage beast. He shook his fist furiously.

  "You call my master a forger?" he shouted. "You yourselves repudiateyour own Constitution, which places the control of army and navy inthe hands of your President? You refuse to honor his signature?"

  "Listen to me, Mr. Von Kettler!" The voice of the Secretary of Statecut like a steel edge. "You totally mistake the temper of the peopleof this country. We don't surrender, even to worthy adversaries, muchless to a gang of common thieves, murderers, and criminals likeyourselves. You have been accorded the privilege you sought, that ofan envoy, and that was straining the point. Show yourself here againafter two minutes have elapsed, and you'll go to the gallows--forkeeps."

  "Dogs!" shouted Von Kettler, beside himself with fury. "Your doom isupon you even at this moment. I have but to wave my arm, andWashington shall be destroyed, and with her a score of other cities. Itell you you are at our mercy. Thousands of lives shall pay for thisinsult to my master. I warn you, such a catastrophe is coming as shallshow you the Invisible Emperor does not threaten in vain!"

  With complete nonchalance the Secretary of State took out his watch."One minute and fifteen seconds remaining. Captain Rennell," he said."At the expiration of that time, put Mr. Von Kettler under arrest. Iadvise you to go back to your master quickly, Mr. Von Kettler," headded, "and tell him that we'll have no dealings with him, now orever."

  * * * * *

  For a moment longer Von Kettler stood glaring; then, with a laugh ofderision and a gesture of the hands he vanished from view. And, thoughthey might have expected that denouement, the members of the Councilleaped to their feet, staring incredulously at the place where he hadbeen. Nothing of Von Kettler was visible, not even the eyes, and theresounded not the slightest footfall.

  Dick sprang forward to the door, but his outstretched arms encounteredonly emptiness. In spite of the Secretary of State's instructions, hewas almost minded to apprehend the man. If he could get him!

  The corridor was empty. A guard of soldiers was at the entrance, butthey did not block the entrance. Even now Von Kettler might be passingthem! Why didn't his feet sound upon the floor? How could a bulky manglide so smoothly?

  Perhaps because Dick was undecided what to do, Von Kettler escapedhim. By the time he reached the guards he knew he had escaped.Suddenly there came an unexpected denouement. Somewhere on the WhiteHouse lawn a guard challenged, fired. The snap of one of the silencedautomatics answered him.

  When Dick and the guards reached the spot, the man was lying in acrumpled heap.

  "An airplane," he gasped. "Invisible airplane. I--bumped into it.Men--in it. The damned dogs!"

  He died. Dick stared around him. There was no sign of any airplane onthe lawn, nothing but the tents of the guards, white in the moonlight,and the grim array of anti-aircraft guns that Dick had placed there.

  But behind the White House, in hastily constructed hangars, were ahalf-dozen of the latest pursuit airships--beautiful slim hulls,heavily armored, with armored turrets containing each a quick-firerwith the new armor-piercing bullets. One of these ships, Dick's own,was kept perpetually warmed and ready to take the air.

  * * * * *

  Dick raced across the lawn, yelled to the startled guard in charge.The mechanics came running from their quarters. Almost by the timeDick reached it the ship was ready.

  He twirled the helicopter starter, and she roared and zoomed, takingan angle of a hundred and twenty-five degrees upward off a runway oftwenty yards. Into the air she soared, into the moonlight, up like anarrow for five hundred feet.

  Dick pulled the soaring lever, and she hung there, buzzing like a beeas her helicopters, counteracting the pull of gravity, held hercomparatively stable. He scanned the air all about him.

  Washington lay below, her myriad lights gleaming. Immediately beneathhim Dick saw the guns and the tents of the soldiers, and the littlegroup that was removing the body of the murdered soldier on astretcher. But there were no signs of any hostile craft.

  Had the murdered man really bumped into an invisible airship, or hadhe only thought he had? Had those devils learned to apply the gas tothe surfaces of airplanes? There was no reason why they should nothave done so.

  But surely the utmost ingenuity of man had not contrived to render amodern plane, with its metalwork and machinery, absolutelytransparent?

  * * * * *

  And, again, how was it possible to have silenced the sound of engines,the whir of a propeller, so that there should be no auditoryindication whatever of a plane's presence?

  Dick looked all about him. Nothing was in the air--he could have swornit. He replaced the soaring lever and banked in a close circle, hisglance piercing the night. No, there was nothing.

  Crash! Boom! The plane rocked violently, tossing upon gusts of air. Ahuge, gaping hole of blackness had suddenly appeared in the middle ofthe White House lawn. The tents were flat upon the ground. Through therising smoke clouds Dick saw tongues of flame.

  No shell that, but a bomb, and dropped from the skies less than fivehundred feet from where Dick hovered. Yet there was nothing visible inthe skies save the round orb of the moon.

  A rush of wind past Dick's face! One of the vanes of the helicoptercrumpled and fluttered away into the night. Dick needed no furtherpersuasion. The dead soldier had not lied.

  Von Kettler had begun the fulfillment of his threat!

  CHAPTER V

  _The Enemy Strikes_

  As Dick's airship veered and side-slipped, he kicked hard on the leftrudder and brought the nose around. Furiously he sprayed the air witha leaden hail from his quick-firer. He heard a rush of wind go pasthim, and realized that his unseen antagonist had all but rammed him.

  Yet nothing was visible at all, save the moon and the empty sky. Hehad heard the rush of the prop-wash, but he had seen nothing, heardnothing else. Incredible as it seemed, the pilot was flying a planethat had attained not merely invisibility but complete absence of allsound.

  Dick side-slipped down, pancaked, and crashed. He emerged from a planewrecked beyond hope of early repair, yet luckily with no injury beyonda few minor bruises. He rushed toward the hangar, to encounter a bevyof scared mechanics.

  "Another plane! Rev one up quick!" he shouted.

  Planes were already being wheeled out, pilots in flying suits andgoggles were striding beside them. Dick ordered one of them away,stepped into his plane, and in a moment was in the air again.

  In the minute or two that had elapsed since the encounter, the enemyhad been active. Crash after crash was resounding from various partsof Washington. Buildings were rocking and toppling, debris strewed thestreets, fires were springing up everywhere. A thousand feet aloft,Dick could see the holocaust of destruction that was being wrought bythe infernal missiles.

  Bombs of such power had been the unattained ambition of everygovernment of the world--and it had been left to the men of theInvisible Emperor to attain to them. Whole streets went into ruin ateach discharge and from everywhere within the city the wailing cry ofthe injured went up, in a resonant moan of pain.

  In the central part of the city, the district about F Street and thegovernment buildings, nothing was standing, except those buildingsfashioned of structural steel, and these showed twisted girders likethe skeletons of primeval monsters, supporting sections of saggingfloors. Houses, hotels had melted into shapeless heaps of rubble,which filled the streets to a depth of a dozen yards, buryingeverything beneath them. Yet here and there could be seen the forms ofdead pedestrians, motor-cars emerging out of the debris, lying inevery conceivable
position; horses, horribly mangled, were shriekingas they tried to free themselves. And yet, despite this ruin, thegeneral impression upon Dick's mind, as he beat to and fro, signalingto his flight to spread, was that of a vast, empty desolation.

  * * * * *

  Further away: where the ruin had not yet fallen, thousands of humanbeings were milling in a mass, those upon the fringes of the crowdperpetually breaking away, other swarms approaching them, so that theentire agglomeration resembled a seething whirlpool turning slowlyupon itself.

  Then of a sudden the strains of the national anthem floated up toDick's ears. A band was playing in the White House grounds. The tunewas ragged, and the drum came in a fraction of a second late, but animmense pride and elation filled Dick's soul.

  "They'll never beat us!" he thought, intensely, "with such a spiritas that!"

  He had signaled his flight to spread, and search the air. He could seethe individual ships darting here and there over the immensity of thecity, but none knew better than he how fruitless their effort was. Andthe marauders had not ceased their deadly work.

  A bomb dropped near the Washington Monument, sending up a huge spoutof dust that veiled it from his eyes. Instinctively Dick shot towardthe scene. Slowly the dust subsided, and then a yell of exultationbroke from Dick's lips. The noble shaft still stood, a slim taperpointing to the skies.

  It was an omen of ultimate success, and Dick took heart. No, they'dnever beat the grim, unconquerable tenacity of the American people.

  Yet the damage was proceeding at a frightful rate. A bomb droppedsquarely on the Corcoran Gallery and resolved it into a heap of sillystones. A bomb fell in the middle of Pennsylvania Avenue, and thehouses on either side collapsed like houses of cards, falling into asulphurous, fiery pit. And still there was nothing visible but the skyand the moon.

  * * * * *

  Dick gritted his teeth and swore as he circled over the site ofdestruction, out of which tiny figures were struggling. He heard theclang of the fire bells as the motor trucks came roaring toward thescene. Then crash! again. Five blocks northward another dense cloud ofdust arose, and the new area of destruction, spreading as swiftly asripples over a pond, joined the former one, leaving a huge, irregularopen space, piled up with masonry and brick in a number of flat-toppedpyramids.

  Into this, houses went crashing every moment, with a sound like theclatter of falling crockery, but infinitely magnified.

  "The devils! The swine!" shouted Dick. "And we gave Von Kettler theprivileges of an ambassador!"

  And Fredegonde was the sister of this devil! The remembrance of thatstruck a cold chill to Dick's heart again. He tried to blot out herpicture from his mind, but he still saw her as she had appeared thatday after the air ride, flushed, smiling, radiant in her dark beauty.

  A murderess and a spy! He cursed her as he banked and circled back. Hewas helpless. He could do nothing. And all Washington would bedestroyed by morning, if the supply of bombs kept up. But there wasmore to come. Suddenly Dick became aware that two of his flight, atwidely separated distances, were going down in flames. Flaming comets,they dropped plump into the destruction below. Another caught fire andwas going down. No need to question what was happening.

  The invisible enemy was attacking his flight and picking off his menone by one!

  He drove furiously toward two of his planes whose erratic movementsshowed that they were being attacked. As he neared them he saw onecatch fire and begin its earthward swoop. Then the fuselage crackledbeside him, and his instrument board dissolved into ruin.Instinctively he went round in a tight bank and loosed hismachine-gun. Nothing there! Nothing at all! Yet his right wing wentragged, and his own furious blasts into the sky, their echoes drownedby the roar of his propeller, were productive of nothing.

  * * * * *

  He shot past the uninjured plane, signalling it to descend. He wasn'tgoing to let his men ride aloft to helpless butchery. Nothing could bedone until some means was discovered of counteracting the enemy'sterrific advantage.

  He darted across the heart of the city to where another of the flightwas circling, waggling his wings to indicate to it to descend. Then onto the next plane and the next, shepherding them. Thank God theyunderstood! They were bunching toward the hangar. Yet another tookfire and dropped, a burning wreck. Half his flight out of commission,and not an enemy visible!

  He was aloft alone now, courting death--instant, invisible death. Hewouldn't descend until that carnival of murder was at an end. But itwas not at an end. Another crash, far up Pennsylvania Avenue, showedan attempt upon the Capitol. Again--again, and a smoking hell wreathedthe noble buildings so that it was no longer possible to see them. Alull, and then a crash nearer the city's heart. Crash! Crash!

  Invisible though the enemy was, it was easy to trace the movements ofthis particular plane by the successive areas of destruction that itleft behind it. It was coming back over Pennsylvania Avenue, droppingits bombs at intervals. It was methodically wiping out an entiresection of Washington.

  Dick drove his plane toward it. There was one chance in a thousandthat, if he could accurately gauge the progress of his invisibleantagonist, he could crash him and go down with him to death. If hecould get close enough to feel his prop-wash! A wild chance, butDick's mind was keyed up to desperation. He shot like an arrow towardthe scene, with a view to intercepting the murderer.

  Then of a sudden he became aware of a curious phenomenon. A black beamwas shooting across the sky. A black searchlight! It came from theflat top of a large hotel that had somehow escaped the universaldestruction, and, with its gaunt skeleton of structural steel showingin squares, towered out of the ruin all about it like an island.

  * * * * *

  It was from here that the black beam started. It spread fanwise acrossthe sky. But it was not merely blackness. It was utter andimpenetrable darkness, cleaving the sky like a knife. Where itpassed, the rays of the moon were extinguished as fire is extinguishedby water.

  A beam of absolute blackness, that pierced the air like a wideningcone, and made the night seem, by contrast, of dazzling brightnessalong either dark border.

  High into the air that dark beam shot, moving to and fro in the sky.Dick, darting toward the spot where he hoped to find his invisibleenemy, found himself caught in it.

  In utter, inextinguishable darkness! Like a trapped bird he fluttered,hurling himself this way and that till suddenly he found himselfblinking in the dazzling light of the moon again, and the black beamwas overhead.

  Crash! Another widening sphere of ruin as the invisible marauderdropped a bomb. Dick cursed bitterly. Trapped in that black beam, hehad lost his direction. The invisible plane had shot past the pointwhere he had hoped to intercept it.

  He flung his soaring lever, and hung suspended in the air. An easymark for the enemy, if he chose to take the opportunity. No matter.Death was all that Dick craved. He had seen half his flight wiped out,and a hundred thousand human beings hurled to destruction. He wantedto die.

  Then suddenly a wild shout came to his ears, as if all Washington hadgone mad with triumph. And Dick heard himself shouting too, before heknew it, almost before he knew why.

  * * * * *

  For overhead, where the inky finger searched the sky, a luminous shapeappeared, a silvery cigar, riding in the void. The finger missed it,and again there was only the moonlight. It caught it again--and againthe whole devastated city rang with yells of derision, hate, and angeras the black beam held it.

  It held it! To and fro that silvery cigar scurried in a franticattempt to avoid detection, and remorselessly the black beam held itdown.

  It held it down, and it outlined it as clearly as a figure on themoving picture screen. Then suddenly there came a flash, followed by adull detonation, and a black cloud appeared, spreading into a flowerof death near the cigar, and at the edge of the black beam. The chee
rsgrew frantic. The anti-aircraft battery in the White House grounds hadgrasped the situation, and was opening fire.

  To and fro, like a trapped beast, the cigar-shaped airplane fled. Onceit seemed to escape. It faded from the edge of the black finger--fadedinto nothingness amid a roar of execretion. Then it was caught andheld.

  Truncated, bounded by an arc of sky, the black finger followed themurderer in his flight remorselessly. And all around him theanti-aircraft guns were placing a barrage of death.

  He was trapped. No need for Dick to rush in to battle. To do so mightcall off that deadly barrage that held the murderer in a ring ofdeath. Hovering, Dick watched. And then, perhaps panic-stricken,perhaps rendered desperate, perhaps through sheer, wanton courage thatmight have commanded admiration under nobler circumstances, theairship turned and drove straight in the direction of the battery,dropping another bomb as she did so.

  * * * * *

  It fell in a crowded street, swarming with spectators who hadclambered upon the fallen debris, and it wrought hideous destruction.But this time there was hardly a cry--no unison of despair such as hadcome to Dick's ears before. The suspense was too tense. All eyeswatched the airship as, seeming to bear a charmed life, she drove forthe White House itself, through a ring of shells that widened andcontracted alternately, with the object of placing a last bombsquarely upon the building before going down in death. And all thewhile the black searchlight held it.

  Dick Rennell was to experience many thrilling moments afterward, butthere was never a period, measurable by seconds, yet seeming to extendthrough all eternity--never a period quite so fraught with suspenseas, hovering there, he watched the flight of that silvery planespeeding straight toward the executive mansion while all around it theshells bloomed and spread. It was over the White House grounds. Thearchies had failed; they were being outmaneuvered, they could not beswung in time to follow the trajectory of the plane. Dick held hisbreath.

  Then suddenly the silvery ship dissolved in a blaze of fire, a showerof golden sparks such as fly from a rocket, and simultaneously thelast bomb that she was to drop broke upon the ground below.

  Down she plunged, instantly invisible as she escaped the finger of theblack beam; but she dropped into the vortex of ruin that she herselfhad created. Into a pit of blazing fire, criss-crossed by fallingtrees, that had engulfed the battery and a score of men.

  Then suddenly Dick understood. He flung home the soaring lever,banked, and headed, not for the White House, but for the flat roof ofthe hotel from which the black searchlight was still projecting itselfthrough the skies. He hovered above, and dropped, light as a feather,upon the rooftop.

  * * * * *

  There was only one person there--an old man dressed in a shabby suit,kneeling before a great block of stone that had been dislodged upwardfrom the parapet and formed a sort of table. Upon this table the oldman had placed a large, square box, resembling an exaggerated kodak,and it was from the lens of this box that the black beam wasprojecting.

  Dick sprang from his cockpit as the old man rose in alarm. He ran tohim and caught him by the arm.

  "Luke Evans!" he cried. "Thank God you've come back in time to saveAmerica!"

  CHAPTER VI

  _The Gas_

  In the Blue Room of the White House the Council listened to old LukeEvans's exposition of his invention with feelings ranging fromincredulity to hope.

  "I've been at work all the time," said the old man, "not far fromhere. I knew the day would come when you'd need me. I put my prideaside for the sake of my country."

  "Tell us in a few words about this discovery of yours, Mr. Evans,"said Colonel Stopford.

  Luke Evans placed the square black case upon the table. "It's simple,like all big things, sir," he answered. "The original shadow-breakingdevice that I invented was a heavy, inert gas, invisible, but almostas viscous as paint. Applied to textiles, to inorganic matter, toanimal bodies, it adheres for hours. Its property is to render suchsubstances invisible by absorbing all the visible light rays that fallupon it, from red to violet. Light passes through all substances thatare coated with this paint as if they did not exist."

  "And this antidote of yours?" asked Colonel Stopford.

  "Darkness," replied Luke Evans. "A beam of darkness that meansabsolute invisibility. It can be shot from this apparatus"--heindicated the box upon the table. "This box contains a minute portionof a gas which exists in nature in the form of a black, crystallinepowder. The peculiar property of this powder is that it is thesolidified form of a gas more volatile than any that is known. Sovolatile is it that, when the ordinary atmospheric pressure of fifteenpounds to the square inch is removed, the powder instantly changes tothe gaseous condition."

  "By pressing this lever"--Evans pointed at the box--"a vacuum iscreated. Instantly the powder becomes a gas, which shoots forththrough this aperture with the speed of a projectile, taking the formof a beam of absolute blackness. Or it can be discharged fromcylinders in such a way as to extend over a large area within a fewminutes."

  "But how does this darkness make the invisible airships luminous?"asked Stopford. "Why does not your darkness destroy all light?"

  "In this way, sir," replied the old inventor. "The shadow-breaking gaswith which the airships are painted confers invisibility because itabsorbs sunlight. But it does not absorb the still more rapid waves,or oscillations which manifest themselves as radio-activity. On thecontrary, it gathers and reflects these.

  "Now Roentgen, the discoverer of the X-ray, observed that if X-raysare allowed to enter the eye of an observer who is in completedarkness, the retina receives a stimulus, and light is perceived, dueto the fluorescent action of the X-rays upon the eyeball.

  "Consequently, by creating a beam of complete darkness, I bring intoclear visibility the fluorescent gas that coats the airships; in otherwords, the airships become visible."

  "If a light ray is nullified upon entering the field of darkness, willit emerge at the other edge as a perfect light ray again?" askedStopford.

  "It will emerge unchanged, since the black beam destroys light byslightly slowing down the vibrations to a point where they are notperceived as light by the human eye. On emerging from the beam,however, these vibrations immediately resume their natural frequency.To give you a homely parallel, the telephone changes sound waves toelectric waves, and re-converts them into sound waves at the otherend, without any appreciable interruption."

  "Then," said Stopford, "the logical application of your method is toplunge every city in the land into darkness by means of this gas?"

  "That is so, sir, and then we shall have the advantage ofinvisibility, and the enemy ships will be in fluorescence."

  "Damned impracticable!" muttered Stopford.

  "You seriously propose to darken the greater part of eastern NorthAmerica?" asked the Secretary for War.

  "The gas can be produced in large quantities from coal tar besidesexisting in crystalline deposits," replied Luke Evans. "It is sovolatile that I estimate that a single ton will darken all easternNorth America for five days. Whereas the concentration would be madeonly in specific areas liable to attack. The gas is distilled withgreat facility from one of the tri-phenyl-carbinol coal-tarderivatives."

  Vice-president Tomlinson was a pompous, irascible old man, but it washe who hit the nail on the head.

  "That's all very well as an emergency measure, but we've got to findthe haunt of that gang and smash it!"

  An orderly brought in a telegraphic dispatch and handed it to him. TheVice-president opened it, glanced through it, and tried to hand it tothe Secretary of State. Instead, it fluttered from his nervelessfingers, and he sank back with a groan. The Secretary picked it up andglanced at it.

  "Gentlemen," he said, trying to control his voice, "New York wasbombed out of the blue at sunrise this morning, and the whole lowerpart of the city is a heap of ruins."

  * * * * *

 
; In the days that followed it became clear that all the resources ofAmerica would be needed to cope with the Invisible Empire. Not a daypassed without some blow being struck. Boston, Charleston, Baltimore,Pittsburg in turn were devastated. Three cruisers and a score of minorcraft were sunk in the harbor of Newport News, where they wereconcentrating, and thenceforward the fleet became a fugitive force,seeking concealment rather than an offensive. Trans-Atlanticsea-traffic ceased.

  Meanwhile the black gas was being hurriedly manufactured. Fromcylinders placed in central positions in a score of cities it wasdischarged continuously, covering these centers with an impenetrablepall of night that no light would penetrate. Only by the glow ofradium paint, which commanded fabulous prices, could official businessbe transacted, and that only to a very small degree.

  Courts were closed, business suspended, prisoners released, perforce,from jails. Famine ruled. The remedy was proving worse than thedisease. Within a week the use of the dark gas had had to bediscontinued. And a temporary suspension of the raids served only toaccentuate the general terror.

  There were food riots everywhere, demands that the Government come toterms, and counter-demands that the war be fought out to the bitterend.

  Fought out, when everything was disorganized? Stocks of food congestedall the terminals, mobs rioted and battled and plundered all throughthe east.

  "It means surrender," was voiced at the Council meeting by one of themembers. And nobody answered him.

  Three days of respite, then, instead of bombs, proclamationsfluttering down from a cloudless sky. Unless the white flag ofsurrender was hoisted from the summit of the battered Capitol, theInvisible Emperor would strike such a blow as should bring America toher knees!

  * * * * *

  It was a twelve-hour ultimatum, and before three hours had passedthousands of citizens had taken possession of the Capitol and filledall the approaches. Over their heads floated banners--the Stars andStripes, and, blazoned across them the words, "No Surrender."

  It was a spontaneous uprising of the people of Washington. Hungry,homeless in the sharpening autumn weather, and nearly all bereft ofmembers of their families, too often of the breadwinner, now lyingdeep beneath the rubble that littered the streets, they had gatheredin their thousands to protest against any attempt to yield.

  Dick, flying overhead at the apex of his squadron, felt his heartswell with elation as he watched the orderly crowds. This was at threein the afternoon: at six the ultimatum ended, the new frightfulnesswas to begin.

  At five, Vice-president Tomlinson was to address the crowds. The oldman had risen to the occasion. He had cast off his pompousness andvanity, and was known to favor war to the bitter end. Dick and hissquadron circled above the broken dome as the car that carried theVice-president and the secretaries of State and for War approachedalong the Avenue.

  Rat-tat, rat-a-tat-tat!

  Out of the blue sky streams of lead were poured into the assembledmultitudes. Instantly they had become converted into a panic-strickenmob, turning this way and that.

  Rat-a-tat-tat. Swaths of dead and dying men rolled in the dust, and,as wheat falls under the reaper's blade, the mob melted away in linesand by battalions. Within thirty seconds the whole terrain was piledwith dead and dying.

  "My God, it's massacre! It's murder!" shouted Dick.

  * * * * *

  They had not even waited for the twelve hours to expire. To and frothe invisible airplanes shot through the blue evening sky, till thelast fugitives were streaming away in all directions like hunted deer,and the dead lay piled in ghastly heaps everywhere.

  Out of these heaps wounded and dying men would stagger to their feetto shake their fists impotently at their murderers.

  In vain Dick and his squadron strove to dash themselves into theinvisible airships. The pilots eluded them with ease, sometimessending a contemptuous round of machine-gun bullets in theirdirection, but not troubling to shoot them down.

  Two small boys, carrying a huge banner with "No Surrender" across it,were walking off the ghastly field. Twelve or fourteen years old atmost, they disdained to run. They were singing, singing the NationalAnthem, though their voices were inaudible through the turmoil.

  Rat-tat! Rat-tat-a-tat! The fiends above loosed a storm of lead uponthem. Both fell. One rose, still clutching the banner in his hand andwaved it aloft. In a sudden silence his childish treble could beheard:

  My country, 'tis of thee Sweet land of lib-er-ty--

  The guns rattled again. Clutching the blood-stained banner, he droppedacross the body of his companion.

  Suddenly a broad band of black soared upward from the earth. Those incharge of the cylinders placed about the Capitol had released the gas.

  A band of darkness, rising into the blue, cutting off the earth,making the summit of the ruined Capitol a floating dome. But, fast asit rose, the invisible airships rose faster above it.

  A last vicious volley! Two of Dick's flight crashing down upon thepiles of dead men underneath! And nothing was visible, though thedarkness rose till it obliterated the blue above.

  * * * * *

  At dawn the Council sat, after an all-night meeting. Vice-presidentTomlinson, one arm shattered by a machine-gun bullet, still occupiedthe chair at the head of the table.

  Outside, immediately about the White House, there was not a sound.Washington might have been a city of the dead. The railroad terminals,however, were occupied by a mob of people, busily looting. There wasgreat disorder. Organized government had simply disappeared.

  Each man was occupied only with obtaining as much food as he couldcarry, and taking his family into rural districts where the Terrorwould not be likely to pursue. All the roads leading out ofWashington--into Virginia, into Maryland, were congested with columnsof fugitives that stretched for miles.

  Some, who were fortunate enough to possess automobiles, and--what wasrarer--a few gallons of gas, were trying to force their way throughthe masses ahead of them; here and there a family trudged beside apack-horse, or a big dog drew an improvised sled on wheels, loadedwith flour, bacon, blankets, pillows. Old men and young childrentrudged on uncomplaining.

  The telegraph wires were still, for the most part, working. All theworld knew what was happening. From all the big cities of the East asimilar exodus was proceeding. There was little bitterness and littledisorder.

  It was not the airship raids from which these crowds were fleeing.Something grimmer was happening. The murderous attack upon thepopulace about the Capitol had been merely an incident. This laterdevelopment was the fulfilment of the Invisible Emperor's ultimatum.

  Death was afield, death, invisible, instantaneous, and inevitable.Death blown on the winds, in the form of the deadliest of unknowngases.

  * * * * *

  In the Blue Room of the White House a score of experts had gathered.Dick, too, with the chiefs of his staff, Stopford, and the army andnaval heads. Among them was the chief of the Meteorological Bureau,and it was to him primarily that Tomlinson was reading a telegraphicdispatch from Wilmington, South Carolina:

  "The Invisible Death has reached this point and is working havocthroughout the city, spreading from street to street. Men are droppingdead everywhere. A few have fled, but--"

  The sudden ending of the dispatch was significant enough. Tomlinsonpicked up another dispatch from Columbia, in the same State:

  "Invisible Death now circling city," he read. "Business sectionalready invaded. All other telegraphists have left posts. Can't sayhow long--"

  And this, too, ended in the same way. There were piles of suchcommunications, and they had been coming in for eighteen hours. Atthat moment an orderly brought in a dozen more.

  Tomlinson showed the head of the Meteorological Bureau the chart uponthe table. "We've plotted out a map as the wires came in, Mr. Graves,"he said. "The Invisible Death struck the southeast shore of the UnitedStat
es yesterday afternoon near Charleston. It has spreadapproximately at a steady rate. The wind velocity--?"

  "Remains constant. Seventy miles an hour. Dying down a little,"answered Graves.

  "The death line now runs from Wilmington, South Carolina, straight toAugusta, Georgia," the Vice-president pursued. "Every living thingthat this gas has encountered has been instantly destroyed. Men,cattle, birds, vermin, wild beasts. The gas is invisible andinodorous. These gentlemen believe it may be a form of hydrocyanicacid, but of a concentration beyond anything known to chemistry, sodeadly that a billionth part of it to one of air must be fatal,otherwise it could not have traveled as it has done. Warnings havebeen broadcasted, but there are no stocks of chemicals that mightcounteract it. Flight is the only hope--flight at seventy miles anhour!"

  * * * * *

  His voice shook. "This gas has been loosed, as you told us, upon thewings of the hurricane that came through the Florida Strait. What arethe chances of its reaching Washington?"

  "Mr. Vice-president, if the wind continues, and this gas hassufficient concentration, it should be in Washington within the nexteight hours." Graves replied. "If the wind changes direction,however, this gas will probably be blown out to sea, or into theAlleghanies, where it will probably be dissipated among the hills, orby the foliage on the mountains. I'm not a chemist--"

  "No, sir, and I am not consulting you as one," answered old Tomlinson."A death belt several hundred miles in length and three or fourhundred deep has already been cut across this continent. We are facedwith wholesale, unmitigated murder, on such a scale as was never knownbefore. But we are an integral part of America, and Washington has nomore right to expect immunity than our devastated Southern States. Thequestion we wish to put to you is, can you trace the exact coursetaken by the hurricane?"

  "I can, Mr. Vice-president," answered Graves. "It originated somewherein the West Indian seas, like all these storms. We've been getting ourreports almost as usual. Our first one came from Nassau, which wasbadly damaged. The storm missed the Florida coast, as many of them do,and struck the coast of South Carolina--in fact, we received a reportfrom Charleston, which must have almost coincided with your firstreport of the gas."

  "If the storm missed the Florida coast, it follows that the gas wasnot discharged from any point on the American continent," saidTomlinson. "From some point off Florida--from some island, or from aplane or from a ship at sea."

  "Not from a ship at sea, Mr. Vice-president," interposed the head ofthe Chemical Bureau. "To discharge gas on such an extensive scalewould require more space than could be furnished by the largestvessel, in my opinion."

  "In all probability the gas was 'loaded,' so to say, onto the galesomewhere in the Bahamas," said Graves. "That seems to me the mostlikely explanation."

  * * * * *

  Vice-president Tomlinson nodded, and picked up one of the latesttelegraphic dispatches, as if absently.

  "Gentlemen," he said, "the Invisible Death has already reachedCharlotte."

  He picked up another. "Reported Abaco Island, Bahamas, totally wreckedby storm. All communication has ceased," he read. He turned to Dickand spoke as if inspired. "Captain Rennell, there is yourdestination," he thundered. "They've betrayed themselves. We've gotthem now. You understand?"

  "By God, sir! It's from Abaco Island, then, that those devils havebeen carrying on their game of wholesale murder!"

  Suddenly a contagion of enthusiasm seemed to sweep the wholeassemblage. Every man was upon his feet in an instant, white,quivering, lips opened for speech that trembled there and did notcome.

  It was Secretary Norris spoke. "The Vice-president has hit the mark,"he said, with a dramatic gesture of his arm. "Yes, they've betrayedthemselves. Their headquarters are on Abaco Island. It's one of thelargest in the Bahamas." He turned to the Secretary for the Navy. "Youcan rush the fleet there, sir?" he asked.

  "Within forty-eight hours I'll have every vessel that can float offAbaco Island."

  "I'll concentrate all airplanes. Take your flight, Captain Rennell.We'll stamp out that nest of murderers if we blow Abaco Island to thebottom of the sea. It can be done!"

  "It can be done, sir--with Luke Evans and his invention," answeredDick.

  CHAPTER VII

  _On the Trail_

  Three hours later, about the time when the war council rose aftercompleting its plans, a sudden shift of the wind blew the poison gasout to sea, just when it appeared certain that it would reach thecapital of the nation.

  The southern half of Virginia had been swept over. Operators,telegraph and telephone, staying at their posts had sent in constantmessages that had terminated with an abruptness which told of thetragic sequel. Yet, at that distance from its source, the intensity ofthe gas had been to some extent dissipated.

  Poisonous beyond any gas known, so deadly as to make hydrocyanic gasinnocuous in comparison, still as it was swept northward on the wingsof the wind, there had been an increasing number of non-fatalcasualties. The most northernly point reached by the gas was Richmond,and here some fifty per cent of those stricken had suffered paralysisinstead of death.

  But a new element had been injected into the situation. Even theheroic courage shown by the populace in the beginning had had itslimits. The morning after the news of the Invisible Death's advent wasmade public mobs had gathered in all the large cities of the East,demanding surrender.

  The submerged elements of crime and disorder had come to the surfaceat last. Committees were formed, with the avowed object of yielding tothe Invisible Emperor, and averting further disaster. In Washington, acity of the dead, half the members of Congress and the Senators hadgathered in the ruined Capitol, to debate the situation.

  There were rumors of an impending march on the White House, of a coupd'etat.

  * * * * *

  The action of the Government was prompt. Five hundred loyalists wereenrolled, armed, and posted round the White House: every avenue ofapproach was commanded by machine-guns. Meanwhile the news was spreadby radio that the headquarters of the Invisible Emperor had beenlocated, and that a strong bombing squadron was being dispatched todestroy it.

  The entire fleet was to follow, and it was confidently anticipatedthat within a little while the Terror would be at an end.

  Those at the white House were less sanguine. There was none butrealized the diabolical strength of their antagonists.

  "Everything depends upon the outcome of the next forty-eight hours,and everything depends on you, Rennell," said Secretary Norris toDick, as he stood beside his plane. Behind him his flight of a dozenairships was drawn up.

  "Find them," added the Secretary; "cover Abaco Island with the blackgas, and the navy and the marines will wipe up the mess that you leavebehind you. God help you--and all of us, Rennell!"

  He gripped Dick's hand and turned away. Dick was very sober-minded ashe climbed into his cockpit. He knew to the full how much dependedupon himself and Luke Evans. Already the shouts of the insurgents wereto be heard at the ends of the barriers, commanded by themachine-guns, and patrolled by the enlisted volunteers.

  Negro mobs were building counter-barricades of their own with rubblefrom the fallen edifices. Civil war might be postponed foreight-and-forty hours, but after that unless there was news ofvictory, the whole structure of civilization would be smashedirreparably.

  It was up to Dick and Luke Evans, and they had assumed such aresponsibility as rarely falls to the lot of man in war.

  * * * * *

  Dick was to lead the flight in a two-seater Barwell plane. This wasone of the latest types, and had been hurriedly adapted to the purposefor which it was to be used. Dick himself occupied the rear seat, withits dual controls, and the gun in its armored casing. In front sat oldLuke Evans, in charge of the black gas projector.

  His famous camera box, containing a minute quantity of gas in slowcombustion, and projecting the bl
ack searchlight, had been built intothe plane. In the rack beside him were a number of the black gasbombs, each of which, dropped to earth, would release enough gas tocover a considerable area with darkness. Both Luke and Dick worerespirators filled with charcoal and sodium thio-sulphate, and besideDick a cage containing three guinea-pigs rested.

  These little rodents were so sensitive to atmospheric changes that aquantity of hydrocyanic acid too minute to affect a man would produceinstantaneous death on them.

  From its hiding-place off the Virginia coast the American fleet wassteaming hotly southward toward Abaco Island, cruisers, destroyers,submarines. That Abaco was British territory had simply not beenconsidered in this crisis of history.

  The twelve airships that followed Dick's contained enough bombs to putthe headquarters of the Invisible Empire out of business for good. Thenaval guns would complete the same business.

  All day Dick and Luke Evans flew southwestward. At first glance,everything appeared normal. The catastrophe that had fallen upon theland was visible only in the shape of the lines of tiny figures,extending for miles, that choked all the roads radiating out of theprincipal cities. It was only when they were over the southern portionof Virginia that the ravages of deadly gas became apparent.

  Flying low, Dick could see the fields strewn with the bodies of deadcattle. Here and there, at the doors of farmhouses, the inmates couldbe seen, lying together in gruesome heaps, caught and killedinstantaneously as they attempted flight. Here, too, were figures onthe roads. But they were figures of dead men and women.

  * * * * *

  They strewed the roads for miles, lying as they had been trapped--men,women, children, horses, mules, and dogs. The spectacle was anappalling one. Dick set his jaws grimly. He was thinking that theCouncil had let Von Kettler escape. He was thinking of Fredegonde. Buthe would not let himself think of her. She deserved no more pity thanthe rest of the murderous crew.

  Over the Carolinas the conditions were still more appalling. Heredeadly gas had struck with all its concentrated power. A citymaterialized out of the blue distance, a factory town with allchimneys spiring upward into the blue, a section of tall buildingsintersected by canyonlike streets, around it a rim of trim houses,bungalows, indicative of prosperity and comfort. And it was a city ofthe dead.

  For everywhere around it, on all the roads, the dead lay piled on topof one another. For miles--all the inhabitants, rich and poor,business men, factory hands, negroes. There had been a mad rush as thefatal gas drove onward upon its lethal way, and all the fugitives hadbeen overwhelmed simultaneously.

  Here were golf links, with little groups strewn on the grass andfairways; here, at one of the holes, four men, their putters still intheir hands, crouched in death. Here was the wreckage of a train thathad collided with a string of freight cars at an untended switch, andfrom the shattered windows the heads and bodies of the dead protrudedin serried ranks.

  Dick looked back. His flight was driving on behind him. He guessedtheir feelings. They had sworn, as he had sworn, that none of themwould return without stamping out that abomination from the earthforever.

  * * * * *

  He signaled to the flight to rise, and zoomed upward to twelvethousand feet. He did not want to look upon any more of those horrors.At that height, the peaceful landscape lay extended underneath, in achecker-board of farms and woodlands. One could pretend that it wasall a vile dream.

  He avoided Charleston, and winged out above the Atlantic, striking astraight course along the coast toward the Bahamas. The shores ofGeorgia vanished in the west. Dick began to breathe more freely. Hismind shook off its weight of horror. Only the blue sea and the bluesky were visible The aftermath of the gale remained in the shape of astrong head breeze and white crests below.

  Dick glanced at the guinea-pigs. They were busily gnawing theircabbage and carrots. The gas had evidently been entirely dissipated bythe wind.

  Toward sunset the low jutting fore-land of Canaveral on the east coastof Florida, came into view. Dick shifted course a little. Three hoursmore should see them over Abaco.

  His flight had explicit instructions. As soon as the black gas hadrendered visible the headquarters of the Invisible Emperor, they wereto circle above, dropping their bombs. When these were exhausted, themachine guns would come into play. There was to be no attention paidto signals of surrender. They were to wipe out the headquarters, tokill every living thing that showed itself--and the navy and themarines would mop up anything left over.

  The sun went down in a blaze of gold and crimson. Night fell. The moonbegan to climb the east. The black sea, stretching beneath, was asempty as on the day when it was created. Nothing in the shape ofnavigation appeared.

  Two hours, three hours, and old Evans turned round in his cockpit andpointed. On the horizon a black thread was beginning to stretchagainst the sky. It was Abaco Island, in the Bahama group. They werenearly at their destination. An hour more--perhaps two hours, and thedeadly menace that threatened America might be removed forever. Dickbreathed a silent prayer for success.

  * * * * *

  They were over Abaco. A long, flat island, seventy miles or so inextreme length, and fairly wide, covered with a dense growth oftropical brush and forest, with here and there open spaces, near theseacoast an occasional farm-house. Dick dropped to five thousand, tothree, to one. The moon made the whole land underneath as bright asday.

  There were no evidence of destruction by the hurricane. The farmhousesstood substantial and well roofed. If death had struck Abaco Island,it had been the work of man, not Nature.

  Dick zoomed almost to his ceiling, until, in the brilliant moonlight,he could see Abaco Island from side to side. For the most part it washeavily wooded with mahogany and lignum vitae: toward the centralportion there was open land, but there was not the least sign of anyconstruction work.

  Again he swooped, indicating to his flight to follow him. At athousand feet he examined the open district intently. Here, ifanywhere upon the island, the Invisible Emperor had his headquarters.Was it conceivable that a gas factory, hangars, ammunition depotscould exist here invisibly, when he could look straight down upon theground?

  Dick's heart sank. The hideous fear came to him that Graves had beenmistaken, that he had come on a wild-goose chase. This could not bethe place. It was quite incredible.

  Again and again he circled, studying the ground beneath. Now he couldsee that the tough grass and undergrowth marked curious geometricalpatterns. Here, for example, was an oblong of bare earth around whichthe vegetation grew, and it was obviously the work of man.

  Here were four squares of bare ground set side by side, with thinstrips of vegetation growing between them.

  Then of a sudden Dick knew! Those squares and parallelograms of bareground indicated the foundations of buildings. _He was looking down onthe very site of the Invisible Emperor's stronghold!_

  He shouted, and pointed downward. Luke Evans looked round and nodded.He understood. He patted the camera-box with a grim smile on his oldface.

  CHAPTER VIII

  _The Magnetic Trap_

  Upon those squares and oblongs of bare earth, incredible as it seemed,rose the structures of the Invisible Empire, themselves both invisibleand transparent, so that one looked straight down through them and sawonly the ground beneath them.

  Every interior floor and girder must have been treated with the gas.They had been cunning. They must have discovered some permanent meansof charging paint with the shadow-breaking gas, so that the buildingswould remain invisible for months and years instead of hours.

  But they had not been cunning enough. It had not occurred to them thatthe foundations would still be visible underneath, for the simplereason that grass does not grow without sunlight.

  Dick saw old Luke Evans nodding and pointing downward. The old manpicked up his end of the speaking-tube, but Dick ignored the gesture.He signaled to his flight to
rise, and zoomed up, circling, andstudying the land beneath.

  That oblong was evidently the central building. Those four squaresprobably housed airplanes, and each would hold half a dozen. Thatelliptical building might contain a dirigible. That round patch wasprobably the gas factory.

  Now Dick could see more patches of bare ground, extending in thedirection of the sea. He gunned his ship and followed the gap amongthe trees to the ocean, a few miles distant. Yes, there were moreevidence of activity here. Beside the water, in what looked like adeep natural harbor, was what seemed to be the foundations of a dock.Perhaps even vessels of war floated on the phosphorescent Bahama sea.

  * * * * *

  He circled back, his flock wheeling like a flight of birds andfollowing him. He signaled to them to scatter. They had certainly beenobserved; at any moment a hail of lead might assail them invisibly outof the air. They must get to work quickly. But had they understood thesignificance of those bare patches?

  Dick saw Luke Evans still fidgeting impatiently with his end of thespeaking-tube, and picked it up.

  "I'm thinking, Captain Rennell, we've got no time to lose if we wantto keep the upper hand of those devils," called the old man.

  "Yes, you're right," Dick answered. "Lay a trail of gas bombs allaround those hangars and buildings, enough to hold them dark for sometime. And keep a bomb or two in reserve."

  Luke Evans shouted back. The plane was again above the structures. Theold man dropped a bomb over the side, and Dick zoomed again, hisflight wheeling up behind him.

  Higher and higher, banking and going round in a succession of tightspirals, Dick flew. Every moment he expected the blow to fall. As herose, Luke Evans dropped bomb after bomb. A thousand feet beneath theflight was taking up positions, hovering with the helicopters, lookingup to Dick for the signal, and waiting.

  Then from beneath the cloud of black gas began to rise, as Luke Evansdropped his bombs. It filled the lower spaces of the sky, blotting outthe land in impenetrable darkness. That darkness, above which Dick andhis flight were soaring, rose like a solid wall, built by someprehistoric race that aimed to fling a tower into the heavens.

  * * * * *

  And then--the miracle! Dick gasped in sheer delight as he realizedthat he had made no mistake.

  At first all he could see was a number of criss-crossingphosphorescent lines that appeared shimmering through the blacknessunderneath. They ran luminously here and there, forming no particularpattern, much like the figures on the radium dial of a watch whenfirst they come into wavering visibility at night.

  Then the lines began to intersect one another, to assume geometricpatterns and curves. And bit by bit they took meaning andsignificance.

  And suddenly the whole invisible stronghold lay revealed upon theground beneath, a shining, dazzling play of weaving light.

  Buildings and hangars stood out, clearly revealed; the rounded vaultof a dirigible hangar, and the shining ribbon of a road that ranthrough a pitch-dark tarmac, and was evidently constructed from somegas-impregnated materials. On this tarmac was a flight of shiningairplanes, ready to take off. There were the odd, ovoid figures of theaviators in their silken overalls. More figures appeared, running outfrom the buildings. It was clear that the sudden raid had taken themall by surprise.

  Luke Evans yelled and pointed. "We've got them now, sir!" Dick heardabove the whine of the helicopter engine. "We've--"

  But of a sudden the old man's voice died away, though his mouth wasstill moving.

  Dick leaned out of his cockpit and fired a single red Very light, thesignal for the attack. And from each plane of his flight, beneath him,a bomb slid from its rack and went hurtling down upon the gang below,while the airplanes circled and hovered, each taking up its station.

  * * * * *

  Dick was too late. By a whole minute he had missed his chance. Herealized that immediately, for before the red light had flared fromhis pistol, the hostile planes were in the air. He had flown too low,and given the alarm.

  It meant a fight now, instead of a mad dog destruction, and Dick didnot underestimate the power of the enemy. But he felt a thrill offurious satisfaction at the prospect of battle. From every plane thebombs were falling. Underneath, ruin and destruction, and leapingflames--and yet darkness, save for the phosphorescent outlines of thebuildings.

  And the lines of these were broken, converging into strangecriss-crosses of luminosity, as the beams fell in shapeless heaps.Dark fire, sweeping through the headquarters of the Invisible Emperor,a veritable hell for those below! A taste of the hell that they hadmade for others!

  Then a strange phenomenon obtruded itself upon Dick's notice. _Nothingwas audible!_ The bombs were falling, but they were falling silently.No sound came up from beneath. And, except for the throbbing of hisengine, Dick would have thought it had stopped. He could no longerhear it.

  That terrific holocaust of death and destruction was inaudible.Skimming the upper reach of the air, high above that wall of darkness,Dick saw old Luke Evans pick up his end of the speaking-tube, andmechanically followed suit. He could see the old man's lips moving.But he heard nothing!

  And now another phenomenon was borne in on his notice. His flight wereperhaps five hundred feet beneath him, hovering a little above thebarrage of black gas. But they were converging oddly. And there was nosight of the airplanes that Dick had just seen taking off from theinvisible tarmac.

  * * * * *

  Dick fired two Very lights as a signal to his flight to scatter. Whatwere they doing, bunching together like a flock of sheep, when at anymoment the enemy planes might come swooping in, riddling them withbullets? He thrust the stick forward--and then realized that hiscontrols had gone dead!

  He thought for a moment that a wire had snapped. But the stickresponded perfectly to his hand, only it had no longer control overhis plane. He kicked right rudder, and the plane remained motionless.He pushed home the soaring lever, to neutralize the helicopter and theplane still soared.

  Then he noticed that the needle of his earth-inductorcompass-indicator was oscillating madly, and realized that it was nothis plane that was at fault.

  Underneath him, his flight seemed to be milling wildly as the shipsturned in every direction of the compass. But not for long. They werenosing in, until the whole flight resembled an enormous airplaneengine, with twelve radial points, corresponding to their propellers,and the noses pointing symmetrically inward, like a herd of game,yarding in winter time.

  And now the true significance came home to Dick. A vertical line ofmagnetic force, an invisible mast, had been shot upward from theground. The airplanes were moored to it by their noses, as effectivelyas if they had been fastened with steel wires.

  And he, too, was struggling against that magnetic force that wasslowly drawing him, despite his utmost efforts, to a fixed positionfive hundred feet above his flight.

  * * * * *

  For a few moments, by feeding his engine gas to the limit, Dickthought he might have a chance of escaping. Her nose a fixed point,Dick whirled round and round in a dizzy maze, attempting to break thatinvisible mooring-chain. Then suddenly the engine went dead. He wastrapped helplessly.

  He saw old Evans gesticulating wildly in the front cockpit. The oldman hoisted himself, leaned over the cowling gibbered in Dick's ear.The silent engine had ceased to throb, and the old man's shouts weresimply not translated into sound.

  Suddenly the flight beneath jerked downward, just as a flag jerks whenit is hauled down a pole. They vanished into the dark cloud beneath.At the same time there came a jerk that dropped Dick's plane a hundredfeet, and flung him violently against the rim of the cockpit.

  Another followed. By drops of a hundred feet at a time, Dick was beinghauled down into the darkness underneath him.

  It rushed up at him. One moment he was suspended upon the rim of it,seeing the moon and star
s above him; the next he had been plunged intoutter blackness. Blackness more intense than anything that could beconceived--soundless blackness, that was the added horror of it.Blackness of Luke Evans's contriving, but none the less fearful onthat account!

  And yet, as Dick was jerked slowly downward, slowly a pale visibilitybegan to diffuse itself underneath. The black cloud was beginning toroll away. The luminous lines began to fade, and in place of themappeared little leaping tongues of fire. In front of him Dick saw LukeEvans's form begin to pattern itself upon the darkness. He saw theform move sidewise, and caught at Luke's arm as he was about to hurlanother gas bomb. "No!" he shouted--and heard no sound come from hislips.

  * * * * *

  Luke understood. He seemed to be replacing the bomb in the rack.Beneath them now, as they were jerked downward, were fantastic swirlsof black mist, and, at the bottom, a pit of fire that was slowlycoming into visibility.

  Dick uttered a cry of horror! Five hundred feet below his plane he sawthe dim forms of his flight, still bunched together, noses almosttouching. And they were dropping straight into that flaming furnaceof ruin underneath, which was growing clearer every instant.

  Down, jerk by jerk. Down! The black cloud was fast dispersing from theground. The flight were hardly a thousand feet above the fire. Down--along jerk that one! Once more! The flames leaped up hungrily about thedoomed airships. Cries of mad horror broke from Dick's lips as hewitnessed the destruction of ships and men.

  He could see almost clearly now. The twelve ships, still retainingtheir nose-to-nose formation, were in the very heart of the fire.Spurts of exploding gasoline thrust their white tongues upward. Therewas only one consolation: for the doomed men, death must have comepractically instantaneously.

  From where he hung, Dick could feel the fierce heat of the flamesbelow. In front of him, old Luke Evans sat in his cockpit like onepetrified. He was feebly fumbling at his camera-box, as if he had someidea of using it, and had forgotten that it was fixed to the plane,but the old man seemed temporarily to have lost his wits.

  Rushing flames surrounded the burning airships, reducing them to asolid, welded mass of incandescent metal. Dick looked down, waitingfor the next jerk that would summon him to join his men. At the momenthe was not conscious of either fear or horror, only intense rageagainst the murderers and regret that he could never bring back thenews of victory.

  * * * * *

  The cloud had almost dissipated. In place of the phosphorescence,electric lights had appeared, making the ground beneath perfectlyvisible. Dick could see a number of men grouped together at theentrance to a large building, part of which had been wrecked by abomb, though there were no evidences of fire. Other structures hadbeen dismantled and knocked about, but what remained of them had notbeen charred by fire. Evidently they had been fireproofed. Perhaps thegas itself was incombustible. Only in the middle of the tarmac, wherethe remnants of the airplanes blazed, was there any sign of fire.

  There were three machines resembling dynamos, placed one at eachcorner of the tarmac, equidistant from the central holocaust. Ahalf-dozen men were grouped about each of them, and by the light fromthe huge reflector over each Dick saw that they were whirring busily.At the time it did not occur to him that these were the machines thatwere sending out the electrical force that had held the airplanespowerless.

  But as he looked, his mind still a turmoil of hate and hopeless anger,he saw one of the three machines cease whirring. The group about itdispersed, the light above went out. And now his plane, as if drawn bythe power of the two remaining machines, began to move jerkily again,not down toward the burning wreckage, but sidewise, away from it.

  Straight out toward the side of the tarmac it moved jerked downwarddiagonally, until it rested only a few feet above the ground.

  Then suddenly Dick felt the plane quiver, as if released from thepower of the force that had held it. It nosed down and crashed, rolledover amid the wreckage of a shattered wing. The concussion shot Dickfrom the cockpit clear of the smashed machine.

  He landed upon his head, and went out instantly.

  CHAPTER IX

  _The Invisible Emperor_

  It was the sound of his name, spoken repeatedly, that brought Dickback to consciousness. He opened his eyes, blinking in broad daylight.He stared about him, and the first thing he saw was Luke Evans,regarding him anxiously from a little distance away. He saw that itwas Luke who had spoken.

  He had heard the old man distinctly. The condition of inaudibility wasgone.

  Not that of invisibility. Dick stared about him in bewilderment. For amoment, before he quite realized what had happened to him, he thoughthe had lost his mind. Underneath him was a thick rug, beneath his heada pillow; he could feel both of them, and yet all he could see was theopen country, a clearing with shrubbery on either side, and, beyondthat, a luxurious growth of tropical trees. Under him, to all visualappearance, was the bare ground.

  He moved, and heard the clank of chains. He looked down at himself.His wrists were loosely linked to a chain that seemed to stretch tightinto vacancy and end in nothing. His ankles were bound likewise.

  And both chains appeared to be of solid silver, but thick enough togive them the strength of iron!

  Then he perceived that old Evans was bound in the same way.

  "Rennell! Rennell!" repeated the old man in a sort of whimper. "ThankGod you've come out of it! I was afraid you were dead."

  "What's happened?" asked Dick. "Where are we? Didn't they get us?"

  "They've got us, damn them!" snarled old Evans. "All the rest burnedto cinders, those fine fellows, Rennell! You were thrown unconscious,but none of my tough old bones were hurt. They pulled us out of thewreckage and brought us in here and tied us with these silver chains."

  "In here? But where are we?" demanded Dick, trying to pass his handacross his aching forehead, and realizing that the chain, though itseemed fastened to nothing, was perfectly taut.

  * * * * *

  "In one of their damned invisible houses," whimpered the old man."They're fireproof. Nearly all our bombs fell on the tarmac, and theydid hardly any damage at all. One of those devils was bragging aboutit to me. I couldn't see anything but his eyes. And they've taken awaymy gas-box," wailed old Luke.

  Dick cursed comprehensively and was silent. The burning rage thatfilled him left him incapable of other utterance. Silver chains! Theymust be madmen--yes, that was the only explanation. Madmen who hadescaped from somewhere, obtained possession of scientific secrets, andbanded themselves together to overcome the world. If he could get thechance of a blow at them before he died!

  He heard a door swing open--a door somewhere out on the prairie. Twomen sprang into sudden visibility and approached him. There wasnothing invisible about these men, though they had seemed to havematerialized out of nothing. They wore the same black, trimly fittinguniform that Dick had seen in the White House. They were flesh andblood human beings like themselves.

  "I congratulate you upon your recovery, Captain Rennell," remarked oneof them with ironical politeness. "Also upon your shrewd coup.Needless to say, it had no chance of success, but we were misinformedas to the hour at which you might be expected. We thought it wouldtake the fools at Washington a little longer to puzzle out ourlocation--and then we did not put quite sufficient force into ourhurricane. Quite an artificial one, Captain."

  Dick, glaring at them, said nothing, and the one who had spoken turnedto his companion, laughing, and said something in a foreign languagethat he did not recognize.

  "His Majesty the Emperor commands your presence, and that of this oldfool," said the first man. "Do not attempt to escape us. Death will beinstantaneous." He drew a glass rod from his pocket, the tip of whichglowed with a pale blue light.

  * * * * *

  Again he spoke to his companion, who moved apparently a few feetdistant out on the prairie. Suddenly Dick saw o
ld Evans' chainslacken: then Dick's slackened too. He understood that he was unbound,though his wrists and ankles were still loosely fastened.

  The second man took his station beside Luke Evans and motioned to himto rise. The first man beckoned to Dick to do the same. The twoprisoners got upon their feet, trailing each a length of clankingchain. Each of the two guards covered his captive with the glass rodand motioned to him to precede him.

  Choking with fury, Dick obeyed. He had taken a dozen steps with hisguard uttered a sharp command to halt, at the same time shouting someword of command.

  The edge of a door appeared, also seeming to materialize out of space.It widened, and Dick realized that he was looking at the unpaintedinner side of a door whose outside was invisible. Beyond the doorappeared a flight of steps.

  Dick passed through and descended them. He counted fifteen. He emergedinto a timbered underground passage, well lit with lamps, filled withwhat seemed to be mercury vapor. Behind him walked his guard: behindthe guard he heard Luke Evans shambling. Both chains were clinking,and again Dick's fury almost overcame him.

  He controlled himself. He had no hope or desire for life, but he meantto strike some sort of blow before he died, if it were possible.

  They turned out of the timbered passage, Dick's guard now walking athis side, the glass rod menacing his back. Dick found himself in alarge subterranean room of extraordinary character. The walls were notmerely timbered, but paneled. Pictures hung upon them, there were softrugs underfoot, there was antique furniture. Everything was in plainsight.

  * * * * *

  There was a door at the farther end, from beyond which came the murmurof voices. Two guards in the same black uniform, but without theornamental silver braid, stood to attention, long halberds in theirhands. One spoke a challenge.

  The guard at Dick's side answered. The two men stepped backward, eachabout two feet, and pulled the two cords on either side of a curtainbehind the open door. Dick passed through.

  He stopped in sheer amazement. The gorgeousness of this larger roominto which he entered was almost stupefying. It seemed to have beenlifted bodily from some European palace. Mirrors with gilt edges ranalong the side. On the floor was a single huge rug of Oriental weave.

  At the farther end was a throne of gilt, lined with red velvet inwhich sat a man. An old man, of perhaps eighty years, with a greypeaked beard and fierce, commanding features. On his head was a goldcrown glittering with gems. About him were gathered some twoscore menand a few women.

  Those ranged on either side of the throne wore, like its occupant,robes of red, lined with ermine. The rank behind wore shorter robes,less decorative, but no less extraordinary. They might all havestepped out of some medieval court.

  Behind this second line, and half-encircling them, were officers inthe black uniform with the silver braid.

  There had been chattering, but as Dick passed through into the room itwas succeeded by complete silence. Dick fixed his eyes upon the oldman on the throne.

  He knew him! Knew him for a once famous European ruler who had losthis throne in the war. A man always of unbalanced mentality, who,after living for years in exile, had been reported dead three yearsbefore. A madman who had vanished to make this last attempt upon theworld, aided and abetted by the secret group of nobles who hadsurrounded him in the days of his pomp and power.

  * * * * *

  Old men, all of those in the first line! Madmen too, perhaps, asmadness begets madness. Behind them, younger men, infected by thestrange malady, and enthusiastic for their desperate cause.

  Yes, Dick knew this Invisible Emperor, lurking here in his undergroundpalace. He knew Von Kettler, too, in the second line, close to theEmperor's throne. And, among the women in their robes, groupedpicturesquely about that throne, he knew Fredegonde Valmy.

  Dark-haired beneath her coronet, of radiant beauty, she fixed her eyesupon Dick's. Not a muscle of her face quivered.

  Then only did Dick see something else, which he had not hithertoobserved, owing to its concealment by the robes of those grouped aboutthe Emperor, and the sight of it sent such a thrill of fury throughhim that he stood where he was, unable to speak or move a muscle.

  The throne was set on a sort of dais, with three steps in front of it.The lowest of these steps was hollow. Within this hollow appeared thehead and shoulders of a man.

  An elderly man clothed in parti-colored red and yellow, thetime-honored garment of court fools. He was on his hands and knees,and the round of his back fitted into the hollow of the step, and hada flat board over it, so that the Emperor, in ascending his throne,would place his foot upon it.

  He was kept in that position with heavy chains of what looked likegold, which passed about his neck and arms, and fitted into heavy goldstaples in the wood. And the old man was President Hargreaves of theUnited States!

  * * * * *

  The President of the American Republic, chained as a footstool for theInvisible Emperor, the madman who defied the world. Dick stoodpetrified, staring into the mild face of the old man, still incapableof speech. Then a herald, carrying a long trumpet, to which a squarebanner was attached, strode forward from one side of the grotesqueassemblage.

  "Dog, on your knees when His Majesty deigns to admit you to thePresence!" he shouted.

  The guard at Dick's side prodded him with his glass rod.

  Then the storm of mad fury in Dick's heart released limbs and voice.The cry that came from his lips was like nothing human. He leaped uponthe guard with a swift uppercut that sent him sprawling.

  The glass rod slipped from his hands to the rug, striking the edge ofhis shoe, and broke to fragments. A single streak of fire shot fromit, blasting a black streak across the Oriental rug.

  Dick leaped toward the throne, and the assemblage, as if paralyzed byhis sudden maneuver, remained watching him without moving. Then awoman screamed, and instantly the picturesque gathering had dissolvedinto a mob placing itself about the person of the Emperor, who sprangfrom his throne in agitation.

  Dick was almost at the steps. But it was not at the Emperor that heleaped. He sprang to Hargreaves's side. "Mr. President, I'm anAmerican," he babbled. "We've located this gang, we'll blow them offthe face of the earth. In chains--God, in chains, sir--"

  Dick stumbled over the length of his own chain that he had beendragging behind him--stumbled and fell prone upon the floor. Before hecould regain his feet they were upon him.

  * * * * *

  A dozen men were holding him, despite his mad, frenzied struggles, andas, at length, he paused, exhausted, one of them, covering his headwith a glass rod, looked up at the Emperor, who had resumed his seat.

  Dick calmed himself. Still gripped, he straightened his body, and gavethe mad monarch back look for look. For a moment the two men regardedeach other. Then a peal of laughter broke from the Invisible Emperor'slips. And any one who heard that peal--any one save those accustomedto him--might have known that it was a madman's laughter.

  He flung back his head and laughed, and the whole crowd laughed too.All those sycophants roared and chuckled--all except Fredegonde. Itwas not till afterward that Dick remembered that.

  He stood up. "Dog of an American," he roared, "do you know why youwere brought here? It was because I wanted one Yankee to live and seethe irresistible powers that I exercise, so that he can go back andreport on them to those fools in Washington who still think they candefy me, the messenger of the All-Highest.

  "I tell you that the things I have done are nothing in comparison withthe things that I have yet to do, if your insane government ofpig-headed fools persists in its defiance. It is my plan to send youback to tell them that their President lies bound in gold chains as myfootstool. That the hurricane which spread the gas through southernAmerica was a mere summer zephyr in comparison with the storm that Ishall send next.

  * * * * *
r />   "All the resources of Nature are at my command thanks to theillustrious chemists who have been secretly working for the past tenyears to serve me. I, the All-Highest, have been commanded by theAlmighty to scourge the world for its insolence in rejecting me, andespecially the pig-race of Yankees whose pride has grown so great.Mine is the divinely appointed task to cast down your ridiculousdemocracies and re-establish the divine world-order of an Emperor andhis nobility.

  "That is why I have chosen, to permit so mean a thing as you to live.As for the old fool beside you, who thought to stay my power with hisbox of tricks--his gas-box is already being analyzed by my chemists,and in a few hours the trivial secret will be at my disposal."

  "And that's just where you're wrong," piped old Luke Evans in hiscracked voice. "That gas can't be analyzed, because it contains anunknown isotope, and, as for yourself, you're nothing but a daft oldfool, with your tin-horn trumpery!"

  For a moment the Emperor stood like a statue, staring at old Luke. Theexpression on his face was that of a madman, but a madman throughwhose brain a straggling ray of realization has dawned. It was thelook upon his face that held the whole assemblage spellbound. Thensuddenly came intervention.

  Through a doorway in the side of the hall came one of the officers inblack. He advanced to the foot of the throne and made a deep, hurriedbow, speaking rapidly in some language incomprehensible to Dick.

  The Emperor started, and then a peal of laughter left his lips.

  "Pig of a Yankee," he shouted to Dick, "your contemptible navy's nowapproaching our shores, with a dirigible scout above it. You shall nowsee how I deal with such swine!"

  CHAPTER X

  _The Tricks of the Trade_

  He barked a command, and instantly Dick was seized by two of theguards, one of whom--the one Dick had knocked down--took the occasionto administer a buffeting in the process of overcoming him. For thesight of the honored President of the United States--that kindly oldman straining his eyes to meet Dick's own--in the parti-colored garbof red and yellow, and chained like a beast below the madman's throne,again filled Dick with a fury beyond all control.

  It was only when he had been half-stunned again by the vicious blowsof his captors, delivered with short truncheons of heavy wood, that atlength he desisted from his futile struggle.

  With swimming eyes he looked upon the gathering about the throne,which, again taking its cue from the madman, way roaring with laughterat his antics. And again Dick's eyes encountered those of FredegondeValmy.

  The girl was not smiling. She was looking straight at him, and for amoment it seemed to Dick as if he read some message in her eyes.

  Only for an instant that idea flashed through his mind. He was in nomood to receive messages. As he stood panting like a wild beast atbay, suddenly a filmy substance was thrown over his head from behind.Then, as his face emerged, and the rest of his body was swiftlyenveloped, he realized what was happening.

  They had thrown over him one of the invisible garments. He could feelthe stuff about him, but he could no longer see his own body or limbs.

  From his own ken, Dick Rennell had vanished utterly. Where his legsand feet should have been, there was only the rug, with the burn fromthe glass tube. He raised one arm and could not see arm or fingers.

  In another moment invisible cords had been flung around him. Dick'sefforts to renew the struggle were quickly cut short. Trussedhelplessly, he could only stand glaring at the madman rocking withlaughter upon his tinsel throne. Beside him, similarly bound, stoodLuke Evans, but Dick was only conscious of the old man's presence byreason of the short, rasping, emphatic curses that broke from hislips.

  * * * * *

  The Emperor turned on his throne and beckoned to Von Kettler, whoapproached with a deferential bow.

  "Nobility, we charge you with the care of these two prisoners," headdressed him. "Have the old one removed to the laboratory, and giveorders that he shall assist our chemists to the best of his power intheir analysis of the black gas. As for the other, take him up to thecentral office, and show him how we deal with Yankees and all otherpigs. Show him everything, so that he may take back a correct accountof our irresistible powers when we dismiss him."

  "Come!" barked one of the guards in Dick's ear.

  Dick attempted no further resistance. Convinced of its futility, sickand reeling from the blows he had received, he accompanied his captorsquietly. There was nothing more that he could do, either for PresidentHargreaves or for old Luke, but he still imagined the possibility ofsomehow warning the approaching fleet or the occupants of thedirigible.

  He was led along the passage, past the guards, and up the stairsagain. The top door opened upon vacancy; it closed, and vanished. Dickfelt the rugs beneath his feet, but he was to all appearances standingon a square of bare earth in the middle of a prairie.

  "Come!" barked the guard again, and Dick accompanied him, trailing hissilver chain. Behind came Von Kettler.

  "Here are steps!" said the guard, after they had proceeded a shortdistance.

  Dick stumbled against the lowest step of an invisible flight. Thebreeze was cut off, showing that they had entered a building.Underneath was a large oval of bare ground. Dick found a handrail andgroped his way up around a spiral staircase, four flights of it.

  "Here is a room!"

  * * * * *

  Dick saw that widening edge of door again. The room inside wasperfectly visible, though it seemed to be supported upon air. It was aspheroid, of huge size, with a number of large windows set into thewalls, and it was filled with machinery. About a dozen workmen inblue blouses were moving to and fro, attending to what appeared to bea number of enormous dynamos, but there were other apparatus of whosesignificance Dick was ignorant. The dynamos were whirring with intensevelocity, but not the slightest sound was audible.

  Von Kettler stepped to a switch attached to a stanchion of whitemetal, surmounted by a huge opaque glass dome, and threw it over.Instantly the hum and whir of machinery became audible, the sound offootsteps, the voices of the workmen, and the creak of boards beneaththeir feet.

  "You see, we have discovered the means of destroying sound waves aswell as shadows, and it was a much simpler feat," said Von Kettlerwith a sneer. "Tell them that when you get back to Washington, Yankeepig. Also you might be interested to know that most of your bombs fellon camouflaged structures that we had erected with the intention ofdeceiving you."

  He gestured to Dick to precede him, and halted him at a plain roundiron pipe or rod that rose up through the floor and passed through theroof. It was surrounded by a mesh of fine wire. Attached to it werevarious gauges, with dials showing red and black numbers.

  "This is perhaps our greatest achievement, swine," remarked VonKettler, affably. "You shall see its operations from above." Hepointed to a narrow spiral staircase rising at the far end of theroom. "It is the practical application of Einstein's gravitation andelectricity in field relation. It is by means of this, and the threedynamos on the ground that we were able to neutralize your engineslast night and bring them down where we wanted them. You must be sureto tell the Washington hogs about that."

  * * * * *

  He motioned to Dick to cross the room and ascend the spiral staircase.Following him, he flung another switch similar to the first one, andinstantly all sound within the room was cut off.

  They ascended the winding flight and emerged upon a floor or platform.Dick felt it under his feet, but he could see nothing except theground, far beneath him. He seemed to be suspended in the void. Hestopped, groping, hesitating to advance. Von Kettler's jarring laughgrated on his ears.

  "Don't be afraid, swine," he jeered. "This place is enclosed. There isa shadow-breaking device on every floor, which renders us completemasters of camouflage."

  A switch snapped. Dick found himself instantly in a rotunda, roofedwith glass, sections of which were raised to a height of three or fourfeet from the
wooden base, admitting a gentle breeze. Three or fourmen were moving about in it, but these wore the black uniform with thesilver braid, and Von Kettler's manner was deferential as he addressedthem, jerking his hand contemptuously toward Dick. Grins of derisionand malice appeared on all the faces.

  Save one, an elderly officer, apparently of high rank, who cameforward and raised his hand to the salute.

  "Captain Rennell," he said, "we are at war with your nation, but weare also, I hope, gentlemen." He turned to Von Kettler. "Is itseemly," he asked, "that an officer of the American army should bebrought here in chains and cords?"

  "Excellency, it is His Majesty's command," responded Von Kettler, witha servile smirk that hardly concealed his elation. "Moreover, theAmerican is to witness the forthcoming destruction of the Yankeefleet."

  The elderly officer reddened, turned away without replying. Dicklooked about him.

  * * * * *

  There was less machinery in this room. The iron pillar that he hadseen came through the floor and terminated some five feet above it inanother of the opaque glass domes, filled with iridescent fire. Aboutit was a complicated arrangement of dials and gauges.

  In the centre of the room was a sort of camera obscura. A large hoodprojected above a flat table, and an officer was half-concealedbeneath it, apparently studying the table busily.

  "Come, American, you shall see your navy on its way to destruction,"said Von Kettler, beckoning Dick within the hood.

  The officer stepped from the table, whose top was a sheet of silveredglass, leaving Von Kettler and Dick in front of it. Dick looked. Atfirst he could see nothing but the vast stretch of sea; then he beganto make out tiny dots at the table's end, terminating in minute blursthat were evidently smoke from the funnels.

  "Your ships," said Von Kettler, smiling. "This is the dirigible." Hepointed to another dot that came into sight and disappeared almostinstantly. "They are a hundred and fifty miles away. Explain to yourfriends in Washington that our super-telescopic sights are based upona refraction of light that overcomes the earth's curvature. It issimple, but it happens not to have been worked out until my Mastercommanded it."

  Dick watched those tiny dots in fascination, mentally computing. At anaverage speed of fifty knots an hour, the squadron's steaming rate,they should be off the coast within three hours. The dirigible wouldtake two, if it went ahead to scout, as was almost certain.

  * * * * *

  Dick stepped back from beneath the hood and glanced about him. If onlyhis arms were not bound, he might do enough damage within a fewseconds to put the deadlier machinery out of commission, if only thesilvered mirror. He glanced about him. Von Kettler, interpreting histhought, smiled coolly.

  "You are helpless, my dear Yankee pig," he said. "But there is moreto see. Oblige me by accompanying me up to the top story."

  He pointed to a ladder running up beside the iron pillar through anopening in the roof, and Dick, with a shrug of the shoulders,complied. He emerged upon a small platform, apparently protruding intovacancy. Far underneath he saw the clearing, and two airplanes on thetarmac, the aviators looking like beetles from that height. He lookedout to sea and saw no signs of the fleet.

  "You have heard of St. Simeon Stylites, Yankee?" purred Von Kettler."The gentleman who spent forty years of his life upon a tall pillar,in atonement for his sins? It is His Majesty's desire that you spend,not forty years, but two or three hours up here, meditating upon hisgrandeur, before returning to earth. It is also possible that you willwitness something of considerable interest. Look out to sea!"

  Dick turned his head involuntarily. He heard Von Kettler's laugh,heard the snap of a switch--then suddenly he was alone in the void.

  At that snap of the switch, everything had vanished from view behindhim, the building, even the platform on which he stood. His feetseemed to rest on nothing. Yet below him he could still see theairplanes, and more being wheeled out.

  * * * * *

  A sense of extreme physical nausea overcame him. He reeled, thenmanaged to steady himself. He, too, was invisible to his own eyes.Involuntarily he cried out. No sound came from his lips. He stoodthere, invisible in an invisible, soundless void.

  For what seemed an unending period he occupied himself withendeavoring to obtain the sense of balance. Then, with a great effort,he managed to loosen the cords that bound his right arm to his side. Amighty wrench, and he had slipped them up above his elbow. His rightlower arm was free.

  He extended it cautiously, and his hand encountered a railing.Instantly he felt more at ease. He began moving slowly around in awidening circle, and discovered that the platform was enclosed. Thefurther side was, however, open, and he began sliding forward, foot byfoot, to locate himself. Once his foot slipped over the edge, and hedrew back hastily. He felt on the other side, and discovered that hewas upon what seemed a plank walk, perhaps a hundred and fifty feetabove the ground, with no rail on either side, and some six feet wide.

  Very cautiously he shuffled his way along it. It was solid enough,although invisible, but more than once Dick walked perilously close toone edge or the other. At length he went down on his hands and knees,and proceeded, crawling, until his movements were arrested by what wasunmistakably a door.

  The plank bridge, then, connected the top stories of two buildings,but what the second was, there was no means of knowing. The door wasbarred on the other side, and did not yield an iota to Dick's cautiouspressure. Dick felt the frame. Beyond was glass, reinforced with ironon the outside, the latter metal forming a sort of lattice work.Cautiously Dick began to crawl up the rounded dome.

  * * * * *

  Foot by foot he made his way, clinging to the iron bars, until he feltthat he had reached the point of the dome's maximum convexity. Hewedged his feet against a bar and rested. Only now was it brought hometo him that it would be impossible for him to find his way back to theplank.

  A long time must have passed, for, looking out to sea, he could seethe squadron now, minute points on the horizon, exuding smudges ofsmoke. The dirigible was still invisible. The airplanes had eitherleft the tarmac or had been wrapped in the gas-impregnated cloth, forboth they and the aviators had vanished.

  Suddenly Dick had an odd sensation that the iron was growing warm.

  In another moment or two he had no doubt of it. The iron bar heclutched was distinctly warm; it was growing hot. He shifted his graspto the adjacent bar and even in that moment the heat had increasedperceptibly.

  Suddenly there came a vibration, a sense of movement. Dick was beingswung outward. The whole dome seemed to be dropping into space. He dughis feet and fingers under the hot rods, and felt himself sliding overon his back.

  Back--back, till he was lying horizontally in space, and clutchingdesperately at the iron bar, which was growing hotter every moment.

  The sliding movement ceased. It was as if the whole upper section ofthe glass dome had opened outward. But the heat of the bars wasbecoming unbearable, and gusts of hot air seemed to be proceeding fromwithin.

  Hot or not, Dick's only alternative was to work his way back to thestable portion of the dome, or to frizzle until he dropped throughspace.

  Clinging desperately to the bars, he began working back, reaching frombar to bar with his right hand and dragging his feet, with theclanking chain attached, from bar to bar also.

  * * * * *

  How he gained the base of the dome he was never able afterward tounderstand. The heat had grown intolerable; his hands were blistering.Somehow he reached it. He rested a moment despite the heat. But tofind the plank walk was clearly impossible. In another minute he mustdrop. Better that than to fry there like St. Lawrence on his griddle.

  And then, just when he had resigned himself to that last drop, therecame an unexpected diversion. Almost beside him a window was hungback. A man looked out. Dick saw one of the workmen in the
blueblouses, and, behind him, within the dome, what seemed like an emptyroom.

  Dick was slightly above the man. As his head and shoulders appeared,he let himself go, landing squarely across his back. He slid down hisshoulders through the open window into the interior of the dome.

  The man, flung against the frame of the window by the shock, uttered apiercing cry. Before he could recover his stand, or take in what hadhappened to him, Dick had gained his feet and leaped upon him. Hisright hand closed upon his throat. He bore him to the floor and chokedhim into insensibility.

  CHAPTER XI

  _In the Laboratory_

  Not until the man's struggles had ceased, and he lay unconscious,panting, and blue in the face, did Dick release him. Then he lookedabout him.

  Save for the workman, he was alone in a rotunda, open to the sky, and,as he had supposed, the whole upper portion of the dome had been flungback, leaving an immense aperture into which the sun was shining,flecking the interior with shafts of light. The temperature, despitethe opening of the dome, must have been in excess of a hundred andtwenty-five degrees.

  There was nothing except an immense central shaft, up which ran ahollow pole of glass, cut off by the invisible paint at the summit ofthe dome. The inside of this glass pole was glowing with coloredfires, and it was from this that the intolerable heat came, though itsfunction Dick could not imagine.

  One thing was clear: It was growing hotter each moment. To remain inthat rotunda meant death within a brief period of time.

  _And there was no way out!_ Dick glared around him, searching theglass walls in vain. No semblance of a stairway or ladder, even. Yetthe workman must have entered by some ingress--if only Dick coulddiscover it!

  He began running round the interior of the dome in the brilliantsunshine, searching frantically for that ingress. And it was growinghotter! The sweat was pouring down his face beneath the invisiblegarment.

  Dick was vaguely aware that the silence switch had been thrown in theroom, for his feet made no sound, but the knowledge was latent in hismind. Two or three times he circumnavigated the interior of the dome,like a rat in a trap.

  Then suddenly he saw a section of the flooring rise in a corner, and aworkman in a blue blouse appear out of the trap door.

  * * * * *

  He stood there, his face muscles working as he shouted for hiscompanion, but no sound came from his lips. He looked about him, andsaw the unconscious man beside the window. He started in hisdirection.

  With a shout, Dick hurled himself toward him. And he checked himselfeven as he was about to leap. For he realized that the second workmanneither saw nor heard him.

  Yet some subconscious impression of danger must have reached his mind,for the workman stopped too, instinctively assuming an attitude ofdefense. Dick gathered a dozen links of his wrist-chain in his righthand, leaped and struck.

  The workman crumpled to the floor, a little thread of blood creepingfrom his right temple.

  It was the thing upon which Dick looked back afterward with lesssatisfaction than any other, leaving the two unconscious men in thatroom of death. Yet there was nothing else he could have done. He ranto the trap, and saw a ladder leading down. In a moment he had swunghimself through and closed the trap behind him.

  The material that lined the walls below must have had almost perfectinsulating qualities, for the temperature here was no hotter than inthe Bahamas on a hot summer day. Dick scrambled down the ladder andfound himself in a machine-shop. Nobody was there, and tools of allsorts were lying about, as well as machinery whose purpose he did notunderstand. A pair of heavy pliers and a vise were sufficient to ridDick of his wrist and ankle chains in a minute or two. With a knife heslashed the cords of invisible stuff that bound him. He stood up,cramped, but free.

  He picked up an iron bar that was lying loose on a table beside amachine, and advanced to the staircase in one corner of the shop. Ashe approached it, another workman came running up.

  * * * * *

  Dick stood aside in an embrasure in the wall partly occupied by amachine. The man passed within two feet of him and never saw him. Onlythen did Dick quite realize that he was actually invisible.

  The moment the man had passed him, Dick ran to the staircase. Hedescended one flight; he was half way down another when a yell of painand imprecation came to his ears. He knew that voice: it was LukeEvans's!

  With three bounds Dick reached the bottom of the stairs. He saw alarge room in front of him. No mistaking the nature of this room; itwas an ordinary laboratory, fitted out with the greatest elaboration,and divided into two parts by paneling. And sight and sound were on.

  In the part nearer Dick three men were grouped about a large dynamo,which was sending out a high, musical note as it spun. Levers anddials were all about it, and above it was the base of the glass tubethat Dick had seen above. In the other part were five or six men.Three of them were testing some substance at a table; three more weregathered about old Luke Evans, whose silver chains had been removedand replaced by ropes, which bound his limbs, and also bound him to aheavy chair, which seemed to be affixed to the ground. One of thethree had a piece of metal in a pair of long-handled pliers. It waswhite hot, and a white electric spark that shot to and fro between twoterminals close by, showed where it had been heated.

  Dick started; he recognized one of the three men as Von Kettler. Hemoved slowly forward, very softly, his feet making no sound on thefiber matting that covered the floor.

  * * * * *

  "Did that feel good, American swine?" asked Von Kettler softly, andDick saw, with horror, a red weal on the old man's forehead. "Now youare perhaps in a more gracious mood, Professor? The unknown isotope inthat black gas of yours--you are disposed to give us the chemicalformula?"

  "I'll see you in hell first," raved old Luke Evans, writhing in hischair.

  Von Kettler turned to the man holding the white-hot metal, and nodded.But at that moment a door behind Evans's chair opened, and FredegondeValmy appeared in the entrance. Von Kettler turned hastily, snatchedthe pliers from the man's hand, and laid the metal in a receptacle.

  But the girl had seen the action. She looked at the weal on Luke'sforehead, and clenched her hands; her eyes dilated with horror.

  "You have been torturing him, Hugo!" she cried.

  "Freda, what are you doing in here? Oblige me by withdrawingimmediately!" cried Von Kettler.

  "Where is Captain Rennell?" the girl retorted. "I will know!"

  "He is upstairs, watching the approaching Yankee fleet, and waiting tosee its destruction," returned the other.

  "You are lying to me! He has been killed, and this old man has beentortured!" cried Fredegonde. "I tell you, Hugo Von Kettler, you are nolonger a half-brother of mine! I am through with you!"

  "Unfortunately," sneered Von Kettler, "it is not possible to disposeof a family relationship so easily."

  * * * * *

  "It is cheap to sneer," the girl retorted. "But you sang a verydifferent song when you were in the penitentiary, in terror of death,and you begged me to come and throw you the invisible robe through thebars. You promised me then that you would abandon this mad enterpriseand come away with me. You swore it!"

  "I have sworn allegiance to my Emperor, and that comes first,"retorted Von Kettler. "Oblige me by retiring."

  "I shall do nothing of the sort," cried the girl hysterically. "Whenyou used me as a tool in your enterprises in Washington, you playedupon my patriotism for my conquered country. I thought I wasundertaking a heroic act. I didn't dream of the villainy, thecold-blooded murder that was to be wrought.

  "You've kept me here virtually a prisoner," she went on, with risingviolence, "an attendant upon that old madman, your Emperor, and hissham court, while more murder is being planned. Where is CaptainRennell, I say?" She stamped her foot. "I demand that he and this oldman be set at liberty at once. Hugo," she pleaded, "com
e away with me.Don't you see what the end must be? This is no heroic enterprise, itis wholesale murder that will arouse the conscience of civilizedmankind against you! Order that the vortex-ray be turned off," shewent on, looking through the opening in the partition toward thedynamo. "That gas--you cannot be so vile as to send it forth again, todestroy the American ships?"

  "My dear Freda," retorted the young man coolly, "the vortex-ray isalready charged with the gas, and at a height of twenty thousand feetit is now creating a vacuum that will send the gas upon the wings of ahurricane straight up the Atlantic seaboard. It will obliterate everyliving thing on board the battleships, from men to rats, and this timewe mean to reach New York.

  "As for that swine Rennell," he went on, "you heard His Majestyannounce his intention of sending him back to Washington with theinformation of our irresistible power. Of course I know you are inlove with him, and that these qualms of conscience are due to thatcircumstance."

  * * * * *

  But Dick hardly heard the latter part of Von Kettler's remarks.Suddenly the significance of the dynamo and the superheated room abovehad come home to him. He had read of such a project years before, insome newspaper, and had forgotten about it until that moment.

  By sending a high-tension current almost to the limits of the earth'satmosphere, the article had said, a vortex or vacuum could be set upwhich would create a hurricane.

  The tremendous pressure of the in-rushing air would make a veritablecyclone, which, taking the course of the prevailing winds, would rushforth on a mission of widespread disaster.

  And on this hurricane would go the deadly gas, infinitely diluted, andyet deadly to all life in its infinitesimal proportion to theatmosphere.

  And the American fleet was now approaching the Bahama shores.

  Dick forgot Luke Evans, everything else, as the significance of thatmechanism in the next room came home to him. He ran like a madmanthrough the space in the partition, and, raising the bar aloft,brought it thudding down upon the dials, twisting and warping them.

  He struck at the hollow pole, but, glass or not, it defied all hisefforts. He seized a heavy lever and flung it into reverse--and twoothers.

  Yelling, the three attendants broke and ran. Out of the laboratory thesix came running, collided with the three. Behind them Dick could seeFredegonde Valmy, a knife in her hand, slashing at Luke Evans's bonds.

  Dick swung his bar and brought it crashing down on a head, felling theman like a log. He saw Von Kettler pull one of the glass rods fromhis pocket and fire blindly. The discharge struck a second attendant,and the man dropped screeching, his clothes ablaze.

  Somebody yelled, "He's there! Look at his eyes!" and pointed at Dick'sface.

  * * * * *

  Dick leaped aside and swung the rod again, felling a third man. Theothers turned and ran. Von Kettler in the van, broke through the doorbehind Luke Evans's chair, and disappeared.

  Dick ran back to where the old man was standing beside the girl, thediscarded ropes at his feet. He flung his hood back. "Luke, don't youknow me?" he shouted.

  It was creditable to Luke Evans's composure that, though Dick musthave presented the aspect of nothing more than a face floating in theair, he retained his composure.

  "Sure I know you, Rennell," replied the old man. "And you and me'sgoing to best them devils yet."

  "But the fleet--it's approaching Abaco," Dick cried. "I've got to warnthem."

  Fredegonde seized him by the arm.

  "Come with me," she cried. "If they find you here, they'll kill you."

  Dick hesitated only a moment, then followed the girl as she dashed foranother door on the same side of the laboratory as that by which VonKettler and his men had fled. They dashed down the staircase, and acorridor disclosed itself at the bottom. The girl stopped.

  "There is a private way--the Emperor's," she panted. "He had itconstructed--in case of necessity. I got the keys. I wasplanning--something desperate--to stop these murders; I didn't knowwhat."

  Dick seized her by the arm. "What keys?" he demanded. "The key to theplace where President Hargreaves is?"

  "Yes, but--"

  "We must get him. Where is he?"

  "In a cell beneath the throne room. That's overhead. But they'llcatch us--"

  "Which is the key?" asked Dick.

  The girl produced three or four keys, fumbled with them, handed one toDick. "This way!" she cried.

  * * * * *

  They ran along the corridor. Two guards appeared, moving toward themunder the electric lights. At the sight of the girl running, and LukeEvans, they stopped in surprise.

  Dick had pulled the hood back over his head. He ran toward them,wielding the iron bar. A mighty swing sent the two toppling over, oneunconscious, the other bruised and yelling loudly.

  "Here! Here!" gasped Fredegonde, stopping before a door.

  Dick fitted the key to the lock and turned it. Inside, upon a quitevisible bed, sat President Hargreaves, unchained. He looked upinquiringly as the three entered.

  "Mr. President," said Dick, throwing back his hood, "I'm an Americanofficer, and I want to save you. There's not much chance, but, ifyou'll come with me--"

  Hargreaves got up and smiled. "I'm not a military man, sir," heanswered, "but I'm ready to take that chance rather than--"

  He did not complete the sentence. Shouts echoed along the corridorbehind them. Dick replaced his hood, handed the keys back to the girl."Take Mr. Hargreaves to any place of temporary safety you can," hesaid. "And Mr. Evans. I'll hold them!"

  "It's right here. This door!" panted the girl, indicating a door atthe end of the passage.

  The three ran toward it. Dick turned. Five or six guards with VonKettler at their head, were running toward him. They saw the threefugitives and set up a shout.

  Dick had a quick inspiration. He dashed back into the cell, seized thelight bed, and dragged it through the doorway into the passage, justin time to send Von Kettler and two others sprawling. He brought downthe bar upon the head of one of them, shouting as he did so.

  Then he became aware that the passage was flooded with sunshine.Fredegonde had got the door open.

  He darted back, passed through in the wake of the three, and slammedit shut. Fredegonde turned the key. Instantly Dick found himself withhis three companions upon the prairie. Not a vestige of the buildingswas apparent anywhere, except for the patches of brown earth.

  CHAPTER XII

  _Von Kettler's End_

  Fredegonde took command, repressing her agitation with a visibleeffort. "They cannot break down that door," she said, "and they darenot ask for another key. It will take them a minute or two to go backand reach us around the building. But there may be a score of peoplewatching us. Let us walk quietly toward the thickets. If I am present,they will not suspect anything is wrong."

  But Dick stood still, driven into absolute immobility by theconflicting claims of duty. For overhead, high in the blue, was anAmerican dirigible.

  And at his side was the President of the United States. One or otherof them he must sacrifice.

  He chose. He ran forward without answering. Those squares of brownearth, set side by side, were the airplane hangars, and he meant toseize an airplane, if he could find one beneath its coat ofinvisibility, and fly to warn the dirigible and the fleet.

  A curious wind was blowing. It seemed to come swirling downward, as nowind that Dick had ever known. It was growing in violence each moment,beating upon his face.

  As he ran, he was aware of Luke beside him. He heard shouting allabout them. Luke had been seen. Not only Luke, but Hargreaves, who wasrunning after Luke, with Fredegonde trying in vain to change hisintentions. At the edge of the first brown patch Dick collidedviolently with the wall of the invisible hangar, and went reelingback. The shouts were growing louder.

  "Wait!" gasped Luke Evans. He had something like a large watch in hishand. He held it out like a pistol, and
from it projected a beam ofthe black gas.

  Then Dick remembered Colonel Stopford's words: "He showed me a watchand said the salvation of the world was inside the case. I thought himinsane."

  * * * * *

  Insane or not, old Luke Evans had concealed the tiny model of thecamera-box to good purpose. As he swept the black beam around him, thewhole mass of buildings sprang into luminosity, the figures of a scoreof men, grouped together, and advancing in a threatening mass, somedistance away--and more.

  Two airplanes, standing side by side upon the tarmac, just in front ofthe hangar--not mere pursuit planes, but six-seaters, formidablyarmed, with central turrets and bow and rear guns, and propellersrevolving.

  Two mechanics stood staring in the direction of the little group.

  "I'm with you," gasped Hargreaves. "I'm not a military man, but I'vegot fighting blood, and I come of a fighting race."

  Dick leaped and once more swung the iron bar. The nearer of the twomechanics went down like lead, the second, seeing his companionbludgeoned out of the air, turned and ran.

  Dick shouted, pointing. Fredegonde jumped into the plane, and thePresident scrambled in behind her. The group, dismayed by the blackbeam, which Luke Evans was now turning steadily upon them, had haltedirresolutely. But suddenly a head appeared, moving swiftly through theair toward the plane. It was Von Kettler, with hood flung back, theface distorted with rage and fury.

  At his yells, the whole crowd started forward. Dick leaped into thecentral cockpit, swung the helicopter lever. Something spitted pasthis face, and a long streak appeared on the turret, where thegas-paint had been scored. But he was rising, rising into thatincreasing wind....

  * * * * *

  He heard a yell of triumph behind him. And that yell of Von Kettler'swas his undoing. There is the telepathy between close friends, butthere is also telepathic sympathy between enemies, and in an instantDick understood what that shout of triumph portended.

  He was rising into the line of magnetic force that would anchor hisairplane helplessly, and leave it to be jerked down and held at VonKettler's mercy.

  He released the helicopter lever and opened throttle wide. For aninstant the heavy plane hung dangerously at its low elevation,threatening to nose over. Then Dick regained control, and was wingingaway toward the sea, while yells of baffled fury from behind indicatedthe chagrin of his enemies.

  He glanced up. Thank heaven the dirigible had not approached the trap.It was apparently circling overhead. Of course the observers had seennothing, had no conception that the headquarters of the InvisibleEmpire lay below.

  And yet it seemed to be drifting aimlessly back toward thefleet--erratically, as if not under complete control. And Dick couldsee the ships about a mile offshore, apparently drifting too. Theywere moving as no American squadron ever moved since the day the firsthull was launched, for some of them, turned bow inward toward others,seemed upon the point of collision, while others were lagging on theedge of the formation, as if pointing for home.

  Then suddenly the awful truth dawned upon Dick. The occupants ofships and dirigible alike had been overcome by the deadly gas.

  * * * * *

  Dick banked, turned, leaned forward and shouted to Luke Evans, and,when the old man turned his head, indicated to him to sweep the tarmacwith his ray.

  The thread of black, broadening into a truncated cone, revealednothing save the luminous outlines of the buildings. Apparently thetarmac was deserted. It was queer, too, that the silence of the nightbefore was gone. Dick shouted again, to assure himself of what he knewalready, and heard his own voice again.

  Something had happened, something unexpected----or perhaps the crew ofthe Invisible Emperor, satisfied with the effects of the deadly gas,had not thought it necessary to go to any further trouble.

  Suddenly Dick discovered that he was almost within the circle of theline of magnetic force. Hurriedly he threw over the stick and kickedrudder. It was not till he was again approaching the seashore that itoccurred to him that the force, too, was not in operation.

  He opened throttle wide and shot seaward. He must ascertain what hadhappened, and, if not too late, give warning without delay.

  Then suddenly the vicious rattle of gunfire sounded in Dick's ears,and, materializing out of the sky, came Von Kettler's face. Startledfor an instant, Dick quickly realized that it was Von Kettler in hisplane, with his hood thrown back.

  And Dick realized that his own hood was thrown back. Two faces andnothing else, were the whole visible setting for battle.

  But that look upon Von Kettler's face was even more demoniacal thanbefore. Mad with rage at the prospective escape of his prey, andinfuriated by his half-sister's appearance in the plane, Von Kettlerhad thrown all caution to the winds. In his insane hatred he wasprepared to shoot down Dick's plane and send Fredegonde to destructionwith it.

  * * * * *

  If Dick chose to replace his hood he would have the madman at hismercy. And, if he had thought about it, he would have done so, withFredegonde sitting behind him. But the idea did not enter his mind.Consumed with rage almost equal to Von Kettler's, he only saw therethe face of one of those who had inflicted an unspeakable outrage uponthe President of his country.

  The memory of old Hargreaves, chained before the mock-Emperor'sthrone, enraged Dick more than the holocaust of lives taken by theassassins.

  He shouted a wild answer to Von Kettler's challenge as his plane spedby, and banked. At that moment there came a roaring concussion thatshook the plane from prop to tail.

  Dick turned his head. Somehow, President Hargreaves had contrived toget the rear gun into action, and now he was staring at it as if hecould not believe that he had fired it.

  And that action heartened Dick wonderfully. As Von Kettler's faceappeared again, he loosed his turret gun in a sweeping blast, andheard Von Kettler's gun roar futilely.

  Again they crossed each other's path, and again and again, two faces,only able to gauge roughly the position of their planes. Neither manhad succeeded in injuring the other.

  Once old Lake turned his black ray upon Von Kettler, and for, a momentthe plane stood out luminously in the blackness, but Dick leanedforward and yelled to the old man to desist.

  And once Dick looked back and saw Fredegonde crouched in her cockpitwith eyes wide with terror. And yet he read in her eyes the samedetermination she had expressed in the laboratory. She was throughwith her half-brother.

  * * * * *

  All this while the wind had been increasing, making it difficult tomaneuver the heavy plane; but now, of a sudden there came a dead lull,and then, with a whining sound, the wind rushed in again.

  But this was a wind still more unlike any that Dick had ever known. Amighty gale that revolved circularly, but downward too, like a vortex,catching the plane and sweeping it into an ever tightening circle.

  A man-made gale, upon whose wings the poison gas would spreadnorthward again, carrying unlimited destruction with it. Dick foughtin vain to free himself.

  He was revolving as in a whirlpool, and it required the utmostpresence of mind and watchfulness to hold the plane steady. Round andround he spun--and then, suddenly, out of the void materialized VonKettler's face.

  Von Kettler, helpless too, was spinning round upon the opposite sideof the vortex. Thus each airship was upon the tail of the other, andit was a matter of chance which would get the other within theringsights of the turret gun.

  Von Kettler was so near that his shouts of fury came fitfully toDick's ears as the wind carried them. Dick, working the controls, knewthat not for an instant could he direct his attention from them inorder to fire his gun, and the moment Von Kettler attempted to do so,he was doomed.

  Round and round, struggling, battling in vain--and once more theconcussion of the rear gun shook the plane. And a shout from thePresident reached Dick's ears.
r />   Dick turned his head for an instant, long enough to see Von Kettlerspinning down through the vortex. And he was going down afire.President Hargreaves, "no military man," had got him, the second timehe had ever aligned a gun-barrel upon a target.

  "Bravo, sir, bravo!" Dick shouted.

  And desperately he flung the stick forward and nosed down.

  * * * * *

  No gale, man-made or heaven-made, could carry on its wingsthree-quarters of a ton of armored, turreted airship. Swirling like aleaf, the plane broke through the clutch of the blast. Instantly itgrew calm. Outside that vortex, hardly a breath of air was stirring.It was as if the whole fury of the air was concentrated within thatcircle.

  The ground came rushing up. Once more Dick tried to head seaward. Withflying speed lost, he was calculating the exact moment in his downwardrush when he could hope to resume control. Would that moment comebefore he crashed?

  At less than a hundred feet he partly regained control. For a momentthe plane seemed to fly on an even keel. Then her nose went down asher speed slackened. And this time there was no salvation.

  Working desperately to save her, Dick saw the ground loom up beforehim. He heard the crash as the plane broke into splintering ruin ...he had a last vision of old Luke clutching his precious watch: theneverything was dissolved in darkness....

  CHAPTER XIII

  _You Can't Down the Marines_

  "He's pulling out of it! Keep it up, Gotch!"

  Dick heard the words and opened his eyes. He stared in amazement atthe faces about him. Honest American faces under tropical helmets andabove a uniform that he had never expected to see again. It couldn'tbe real. And yet it was. One word broke from his lips:

  "Marines!"

  "He's got it. Don't let him slip, Gotch.", grinned one of the friendlyfaces, and the man named Gotch, who presumably had some qualificationsfor his job, continued what was meant to be a gentle massage of thenerve centers along Dick's spine.

  "I'm all right." Dick muttered, beginning to realize hissurroundings. He was lying on a strip of prairie near the beach, onwhich the waves were breaking in low ripples about a motorboat thatwas drawn up.

  He sat up. The world was swimming about him, but he seemed to have nobroken bones. Not far away was the wrecked plane, an incongruous massof streaks where the fabric had ripped through the gas-paint. "Whereare the others?" Dick muttered.

  Then he was aware of Fredegonde Valmy lying with a white face under ashrub. Her eyes were open, and turned toward him.

  He heard Luke Evans's voice. The old man hobbled round from Dick'sback, one arm in a bandage.

  "She's hurt rather bad, Rennell, but we won't know how bad till we canget her away," he said. "You've been lying here about an hour, sincewe crashed. President Hargreaves made them take him to the fleet inthe other motorboat to see what he could do. He's assumed command.

  "You see, Rennell, that damn gas caught the fleet and put pretty nearevery man out of commission for good. But these fellows wasn't goingto give up. So, since all their officers were gone, they took two ofthe boats and their arms and equipment, and came ashore to settleaccounts. And they won't believe there's anybody on the island or anybuildings. And I can't make 'em believe it. God, Rennell, thoseinvisible devils may attack us at any moment. I don't understand whatthey're waiting for."

  Gotch spoke: "We know you're Captain Rennell, sir. And this gentleman,we know him too, but he seems a bit queer in his head. Talking of theInvisible Emperor's headquarters on this island, a mile or so inland.The only invisible thing we've found is that piece of a garment wepulled off you."

  "I broke my watch ray machine in the fall, and I can't make thembelieve, Rennell," almost wept old Evans. "Tell them I'm not crazy."

  Dick got upon his feet with an effort, staggered a little, then madehis way to Fredegonde. He kneeled down beside the girl. She wasconscious, and smiled faintly, but she could not speak. He pressed herhand, rose, and came back. "Mr. Evans is not crazy," he said. "Theheadquarters of the gang is over there." He pointed. "Didn't PresidentHargreaves tell you?"

  "He was kind of incoherent, sir." The marines looked at one another,wondering. Was Captain Rennell crazy too?

  "We've had scouts out through the jungle, sir. There's nothing withinfive miles of here. They had a clear view through to the sea from thetop of a hill."

  "I've been there." Dick spoke with conviction. "I must tell youthey've got devices that make them practically irresistible. That gasand other things. And they're invisible. But if you boys are willingto follow me, I'll lead you. It means death. I don't know what they'rewaiting for. But--are you willing to follow me?"

  "We'll follow you, sir"--after a pause, during which Dick read intheir eyes the desire to humor a crazy man. "We'll follow to hell,sir--if that gang's really there."

  "Take your arms, then!" Dick pointed to the stacked rifles.

  A minute later the twenty-odd Marines, forming an open line thatextended from one side of the clearing to the other, were on their waytoward the headquarters of the gang. And Dick, leading them, thoughhis head was reeling, felt as if his own reason was slipping from him.Had he only dreamed all this? Was it possible that the headquarters ofthe Invisible Emperor existed on this desolate prairie? If it wastrue, why had they suddenly become silent, inert? Why had they notlong ago wiped out these few Marines? And the gale--was it nowsweeping northward on its mission of destruction?

  * * * * *

  Half an hour passed. Then the brown patches of the foundations cameinto view upon the open ground. Here were the hangers, here was thecentral building with the Emperor's headquarters. And nothing wasvisible, nothing stirred, yet at any moment Dick expected the rattleof machine-gun bullets or some more terrific method of destruction.

  "Halt!" The line stood still. "I am going forward ahead or you. You'llfollow at a distance of twenty paces. When you see me stop, feel forthe door in the wall, and if I disappear, follow me. You understand?"

  The Marines assented cheerfully. No harm in humoring this poor devilof an officer who had crashed and lost his wits. Like Luke Evans,shambling up through the line to Dick's side. Dick advanced. At anymoment now the concentrated fire of the Emperor's men should blastthem all to smithereens. Nothing happened.

  And it was no dream, for Dick's outstretched hand encountered theexterior wall of the building. He had gauged his way accurately, too,for a step or two brought him to the door. He stepped inside. He wasinside the private door that led to the Emperor's quarters, throughwhich he had passed with Fredegonde, Hargreaves, and Luke Evans intheir flight. It had been broken down, contrary to the girl'spredictions, and the deserted passage within was perfectly visible tothem all.

  Stupefied, the Marines bumped and jostled with each other as theycrowded in. If they had been anything but Marines, their own headsmight have been turned at the discovery of this sudden materializationof a building out of nothingness.

  Being Marines, they only grinned sheepishly, and followed along thecorridor.

  * * * * *

  The first human being they saw was one of the guards, in a blacktunic. He was leaning against a wall, and he was a human being nolonger. He looked as if he was asleep, but he was stone dead, with aplacid look on his face.

  Two more dead guards lay across each other, with smiles on theirfaces: and there was a workman in a blue blouse who had been in atremendous hurry to get somewhere, from his appearance, and had nevergot there. He had fallen asleep instead, and never wakened.

  Dick found a stairway and led the way up. He thought it ran up to thelaboratory, but, instead, the room into which he emerged was theante-room of the Invisible Emperor's audience hall. Six dead guardslay in a heap in front of the curtain, and they had died asunconcerned as their fellows, to judge by the pacific expressions ontheir faces.

  Dick passed through into the throne room. The Marines, behind him, forthe first time uttered exclamations of awe--
of pity.

  The terrific scene that met Dick's eyes would be burned into his braintill his last day.

  Upon his throne, head flung back, sat the Invisible Emperor, hisfeatures set in a sardonic leer of death. And all about him, somesitting, some lying, supporting one another, were his court, officersin black uniforms with the silver braid, and women in court dress. Andall were dead too. But they had not known they had died. They hadfallen asleep--upon the instant that their own volatile gas reachedthem.

  * * * * *

  "I guess that's the explanation, sir," said old Luke Evans. "Thosedevils made the whirlwind and charged it with the gas. But when youreversed that lever, you reversed the process. Instead of projectingthe force outwardly, you made a suction, and every atom of the gasthat hadn't travelled beyond the radius came rushing back and filledthe building. If we'd entered a half-hour later, we'd have been deadones ourselves, but the gas was volatile enough to disperse throughthe chinks and crannies. Anyway, it's all over now."

  Yes, it was all over, Dick thought, as he sat in his deck chair uponthe cruiser that was bearing him northward. The menace to worldgovernment had been destroyed and with it all who had been behind it.There would be a new order in the world, a new and kindliergovernment. Men would feel closer to one another than in the past.Half the personnel of the fleet had escaped the invisible death, andonly one cruiser and the dirigible had been lost in the confusion.There would be a great reception when they put into Charleston.

  Dick bent over Fredegonde, who was asleep in her chair beside him. Theship's surgeon had promised recovery for her. She shouldn't suffer forher half-voluntary part in the business, Dick said to himself. It wasgoing to be his task to help her to forget.

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