The words blurred, and seemed to echo and re-echo inside Hawkes' head. That made twice he'd heard them mention the psi factor--the strange ability a few human minds had to perform seeming miracles. Men who had it could make dice roll the way they wanted. Young girls sometimes had it before puberty, and could throw heavy objects around a room without touching them; they did not even know they were the cause of the motion, but blamed it on poltergeists. Other men caused strange accidents--fires, for instance--the old salamander legend! There'd been a piece of paper--psi equals alpha, the psi factor was the beginning of infinity for mankind. But it had been wrong. He'd changed that, on the other side. It should have read psi equals omega, the absolute end. He gasped hoarsely, and heard their startled voices stop, while the flashlight beam swung around, to pick him out in the darkness. He felt Ellen and her younger brother, Dan, pulling him forward into the little cave with them, and he heard their voices questioning him. But his head was spinning madly under the sudden flood of memories that the missing key word had suddenly brought back. The letter from Professor Meinzer had been about his paper on poltergeists which the old man had seen before publication. He'd been doing research on the psi factor for the government, and he needed a mathematician--even one who proved something which he knew wasn't true, provided the mathematics could handle his theories. Hawkes' head was suddenly brimming with mental images of the seven months, while he worked on the mathematics to tie down the strange pattern of brain waves the old professor had found in the minds of those who had the mysterious psi factor. Dan had worked with them, in the little cluttered apartment, building the apparatus they needed. It was through Dan that Ellen was hired, as a general assistant and secretary. There had been only the four of them, working in deepest secrecy in the three rooms which the government had felt were more suitable to maintain complete security than any deeply buried laboratory could have been. Ellen made a pretense of living there, and it was a neighborhood where no landlady worried about the men who went to a girl's place, provided everything was quiet. They'd succeeded, too--they had found the tiny bundle of cells that controlled the psi factor, and learned to stimulate them by artificial wave trains and hypnosis. But the small group in the top division of the government to whom they were responsible had demanded more proof. * * * * *