Chapter 12

_Von Kettler's End_

Fredegonde took command, repressing her agitation with a visible effort. "They cannot break down that door," she said, "and they dare not ask for another key. It will take them a minute or two to go back and reach us around the building. But there may be a score of people watching 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 the conflicting claims of duty. For overhead, high in the blue, was an American dirigible.

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

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

A curious wind was blowing. It seemed to come swirling downward, as no wind 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 all about them. Luke had been seen. Not only Luke, but Hargreaves, who was running after Luke, with Fredegonde trying in vain to change his intentions. At the edge of the first brown patch Dick collided violently with the wall of the invisible hangar, and went reeling back. The shouts were growing louder.

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

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

* * * * *

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

Two airplanes, standing side by side upon the tarmac, just in front of the hangar--not mere pursuit planes, but six-seaters, formidably armed, with central turrets and bow and rear guns, and propellers revolving.

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've got fighting blood, and I come of a fighting race."

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

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

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

* * * * *

He heard a yell of triumph behind him. And that yell of Von Kettler's was his undoing. There is the telepathy between close friends, but there is also telepathic sympathy between enemies, and in an instant Dick understood what that shout of triumph portended.

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

He released the helicopter lever and opened throttle wide. For an instant the heavy plane hung dangerously at its low elevation, threatening to nose over. Then Dick regained control, and was winging away toward the sea, while yells of baffled fury from behind indicated the 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 seen nothing, had no conception that the headquarters of the Invisible Empire lay below.

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

Then suddenly the awful truth dawned upon Dick. The occupants of ships 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 tarmac with his ray.

The thread of black, broadening into a truncated cone, revealed nothing save the luminous outlines of the buildings. Apparently the tarmac was deserted. It was queer, too, that the silence of the night before was gone. Dick shouted again, to assure himself of what he knew already, and heard his own voice again.

Something had happened, something unexpected----or perhaps the crew of the 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 the line of magnetic force. Hurriedly he threw over the stick and kicked rudder. It was not till he was again approaching the seashore that it occurred to him that the force, too, was not in operation.

He opened throttle wide and shot seaward. He must ascertain what had happened, 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. Startled for an instant, Dick quickly realized that it was Von Kettler in his plane, with his hood thrown back.

And Dick realized that his own hood was thrown back. Two faces and nothing else, were the whole visible setting for battle.

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

* * * * *

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

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

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

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

And that action heartened Dick wonderfully. As Von Kettler's face appeared again, he loosed his turret gun in a sweeping blast, and heard 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 man had succeeded in injuring the other.

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

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

* * * * *

All this while the wind had been increasing, making it difficult to maneuver 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. A mighty 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 spread northward again, carrying unlimited destruction with it. Dick fought in vain to free himself.

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

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

Von Kettler was so near that his shouts of fury came fitfully to Dick's ears as the wind carried them. Dick, working the controls, knew that not for an instant could he direct his attention from them in order 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 the concussion of the rear gun shook the plane. And a shout from the President reached Dick's ears.

Dick turned his head for an instant, long enough to see Von Kettler spinning down through the vortex. And he was going down afire. President Hargreaves, "no military man," had got him, the second time he 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 wings three-quarters of a ton of armored, turreted airship. Swirling like a leaf, the plane broke through the clutch of the blast. Instantly it grew calm. Outside that vortex, hardly a breath of air was stirring. It was as if the whole fury of the air was concentrated within that circle.

The ground came rushing up. Once more Dick tried to head seaward. With flying speed lost, he was calculating the exact moment in his downward rush when he could hope to resume control. Would that moment come before he crashed?

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

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