"I am now sending electro-magnetic waves from the four towers," he resumed. "But instead of broadcasting them in every direction. I am bending them in concave cathode of force over the city. You may picture this cathode as an invisible shield, if you choose, but it is more than that. It it a reflector. If my theories are right, the radio-energetic ray I am about to project upon it from my miniature disc will be flung back to its source as though it had been a ray of light falling on a mirror. The success of the experiment depends upon what the result will be."

Kendrick ceased, moved toward a rheostat.

As he made ready to touch it, a breathless tension settled upon the a.s.semblage. Upon the outcome of what was now to happen rested the fate of America--and the world.

Calmly, though every fiber of his being was at breaking stress, the young scientist opened the rheostat.

For an instant, the ray seared down--then, as it boomeranged back, the disc burst into flame, dissolved, disintegrated. A thin dust, like carbon, slowly settled to the laboratory floor.

Cutting off the current from the radio towers, Kendrick faced them, a light of triumph in his tired eyes.

"You see--it works," he said.

They saw. Beyond a doubt, it worked!

And what Kendrick saw, as his eyes met Marjorie's, made him forget his fatigue.

The rest was a mad scramble of preparation. Only a few brief hours remained, and much was to be done.

The application of the principle that had just been demonstrated involved a hook-up from the Consolidated Electric laboratory with every broadcasting station in the metropolitan area, power being supplied by commandeering every generating plant within a radius of fifty miles.

The city, moreover, had to be evacuated of all but the few brave hundreds who volunteered to stand by their posts at radio stations and generating plants.

As for Kendrick, it was the busiest, most hectic morning he had ever experienced. Only the realization of a girl's love and a nation's trust enabled him to overcome the exhaustion of two sleepless nights.

At length, a little before eleven, all was in readiness. Just two questions troubled the young scientist's mind. Had the people of the disc learned of their preparations to counter the attack? And would the improvised broadcasting apparatus of the area stand the stupendous strain that would be placed upon it if the ray came down?

The first of these questions was answered, staggeringly, at a quarter after eleven.

"Kendrick--oh, my G.o.d!" cried Blake, bursting into the laboratory.

"Marjorie--they've got her again! Look! Read this!"

He thrust out a piece of paper. Kendrick took it, read:

Your daughter will be my queen, after this noon.

"Where'd you get it?" he gasped.

"One of the invisible devils thrust it into my hand right out in the street, not five minutes ago," Blake explained, trembling with anguish. "Do you realize what this means, Kendrick? She's on the disc now--and in a scant three-quarters of an hour...."

"Yes, I realize!" his voice came grimly. "And I realize, too, that they don't know their fate. They'll stay. There's forty-five minutes yet. We can't abandon our defense against the ray, not even for Marjorie. But I'll go, I'll rescue her--or die with her!"

And even as Blake mutely reached out his hand to grip that of the determined young man who stood before him. Kendrick touched his wrist mechanism and went invisible.

Once on the street, he pressed the escalator b.u.t.ton as well--and by the strength of the vibrations that followed, he knew he must be very close within that mysterious lifting zone.

Running west a block, he found it growing stronger.

Fairly racing now, he continued on toward the river, progress unhampered in the deserted streets. Suddenly, with a thrill of exultation, he felt himself swept up, whirled away toward that great shimmering hulk against the sun.

"What hope?" he was thinking. "What possible hope?" And the answer came: Cor!

Reaching the disc, he switched out the escalator influence and hastened across the city to that monumental structure of jade-green stone.

The mighty little dwarf would be up there in his glittering mosaic apartment, or in his pinnacle laboratory, perhaps, ready to pull the lever that would release that stupendous blast of heat.

Gaining the jewelled door of the monarch's quarters at last, after escaping detection by a hair's breadth more than once, he pressed the b.u.t.ton outside, just as the guard had done that first time.

In response, the door opened--and there stood Cor.

He stood there an instant, that is, while the expression on his leathery face went from inquiry to alarm. Then, as Kendrick burst into the room and shut the door, he went invisible.

In that same instant, the young scientist's eyes beheld a sight that caused his heart to leap. There sat Marjorie, bound in a chair, an expression half of hope, half of dejection, on her face.

"It's I--Gordon!" he called. "Take courage!"

"Oh, I prayed so you'd come--and you came!" she murmured as her face lighted. Then, tensely, she added, "The door--look out!"

Kendrick wheeled, and just in time. The door was opening.

"Not so fast!" he called, lunging.

His hands gripped the dwarf, yanked him back, throttled him before he could emit a cry, pushed the door shut.

Cor struggled like a madman, but it was futile. Kendrick's hands cut into his throat like a vice. After a moment or two, he gasped, relaxed.

Releasing his grip then, Kendrick felt for his wrist, stripped off his bracelet--whereupon the dwarf became visible. His face was putty-white. He was either dead or unconscious.

Restoring his own visibility then, he advanced to Marjorie, swiftly freed her.

"Take this!" he said, handing her Cor's bracelet.

She slipped it on.

"Now let's tie him and get out of here. He may be dead, but we can't take any chances."

The dwarf wasn't dead, however, for he groaned and opened his eyes as they lifted him into the chair.

"You win, Professor--but it avails you nothing!" He smiled maliciously. "My capture, my death even, will not prevent the ray. The orders have been given. It will be projected sharp at twelve. You but go to your doom!"