He felt the sickness of futility within him when he remembered the one time he had invaded that other space. He had stepped from the machine and been greeted, cautiously but cordially, by those great-headed super-beings. For days he had been entertained and shown the weird sights of that alien planet. And it wasn't until he woke one night, to see the curious machine hanging motionless over him, its pale blue aura covering his sleeping couch, that he realized that he was being drained of his knowledge subtly every night. He had raced from his sleeping room, fought with the single gun he had taken with him, blasted his way through the screaming mob that tried to hold him captive. He had fought down the long stairs, through the palace door, and had fled into the night, pursued by the men who had protested their friendship. With his last bullet, he had killed the High-Priest, stepped over the prone body, and lurched into his machine. His fingers had flicked the levers on the control panel; there was the instant hum of purring power--and then the machine had whisked him back to his own planet. He had sat for hours in the machine, too drained of energy to move, knowing that only a miracle had saved his machine's secret from the aliens that had planned to use it for an invasion of another space. But now, because of the stupid greed of Jon Vance, because the man did not realize the slavery and terror the aliens would bring to Earth, the machine was gone--and he was a prisoner in the laboratory room. * * * * * He made one final desperate plea. "All right, Vance, if that's the way it is," he said tiredly. "But if anything goes wrong, destroy that machine; those monsters will use it to invade our system." Jon Vance whistled thoughtfully, watching the scientist out of shiny eyes, his heavy features drawn into a frown. Then he shrugged. "If things don't go as planned, maybe I can make a deal," he said. "After all, I always did think I'd like to be a big shot." "You couldn't!" Sheer horror froze Martin into motionlessness. "The hell I couldn't!" Jon Vance stooped, edged through gleaming wires, seated himself at the machine's controls. He twisted a rheostat, closed a switch, grinned at the supine scientist. Kelvin Martin said nothing more, but there was a grim determination replacing the panic in his faded eyes. A vacuum tube swelled with coruscating colors, and a nimbus of light grew from a lacing of wires around the edges of the machine. There was a dull throbbing in the close air, a rushing sense of the releasing of terrible, unknown power. A misty curtain seemed to be drawing tight about the machine's outline. Then the machine was gone from its platform, and Kelvin Martin was alone in the great, bare experimental room. * * * * *