"Well, theories are mighty these days!" beamed Blake, as they rose, clapping the younger man on the shoulder. "You go ahead with your theories--and I'll bring a few facts to bear. To-morrow noon I'll escore some military men and others of my friends over to the laboratory to hear and see something of this menace direct. Meanwhile, and during this crisis, it will honor me to have you as my guest." "Our guest!" amended Marjorie, with a warm smile. * * * * * Next morning Blake motored Kendrick out to the Brooklyn Laboratory of the Consolidated Electric Utilities Corporation and installed him there. Then he left--to return at noon with the promised delegation of generals, admirals, statesmen and financiers. They were all frankly sceptical, though realizing that Henderson Blake was not a man given to exaggeration. Nor did their scepticism altogether vanish when Kendrick had ended his bizarre story with a demonstration of the invisibility device. Murmurs of amazement ran around the laboratory, it is true, but the more hard-headed of his spectators charged him with having invented the apparatus himself. Though they didn't come right out and say so, they seemed to imply that he was seeking publicity. Annoyedly, Kendrick tried to refute their charges. But even as he was summoning words, refutation utter and complete came from the air. A low, humming vibration sounded, grew in volume till it filled the room--and as suddenly ceased: The light of midday faded to twilight. "_The disc!_" gasped Kendrick, rushing to the west windows. They followed, tense with awe. And there, between earth and sun, its myriad towers and spires refracting a weird radiance, hovered that vast flying city. "My God!" muttered a famous general, staring as though he had seen a ghost. A great statesman opened his lips, but no words came. "Appalling! Incredible!" burst from others of that stunned assemblage. * * * * * Their comments were cut short by a broadcast voice, thin and clear, tremendously amplified, a voice Kendrick recognized at once as that of Cor. "People of America!" it said. "We of the planet Vada have come to conquer your country. You will be given forty-eight hours to lay down your arms. If complete surrender has not been made by high noon, two days from now, New York will be destroyed." The voice ceased. The humming recommenced--waned in volume till it died away. Twilight turned once more to midday. Peering fixedly through the west windows of the laboratory, the little assemblage saw the disc swallowed up in the clear blue sky. Then they turned, faced one another gravely. Outside, on the streets, confusion reigned. In newspaper plants, presses were whirling. In telegraph and cable offices, keys were ticking. From radio towers, waves were speeding. Within an hour, the nation and the world knew of this planetary invader and its staggering ultimatum.