He was trembling violently. He ran the last few steps, stumbled into the airlock, and pressed the stud that would seal the door behind him. _We'll come back...._ He heard the massive disk sink home, closing him off. Then he sank down on the floor of the airlock and put his head in shaking hands. After a while he roused himself, closed the inner door of the lock behind him, and walked down the long corridor into the control chamber. The shining banks of keys were there, waiting for his touch; he slumped down before them and listlessly closed the contact of the visiplate. He swung its field slowly, scanning for the last time the bare walls of the underground chamber, making sure that all the spectators had retired out of the way of the blast. Then his clawed fingers poised over the keys, hovered a moment, and thrust down. Acceleration pressed him deep into his chair. In the visiplate, the heavy doors that closed the tunnel above him flashed back, one by one. The energy-charged screen flickered off to let him pass, and closed smoothly behind him. The last doors, cleverly camouflaged, slipped back into place and then dwindled in the distance. It was done. He flashed on out, past the moon, past Mars, over the asteroid belt. The days merged into weeks, then months, and finally, far out, _The Avenger_ curved into an orbit and held it. The great motors died, and the silence pressed in about him. Already he could feel the invisible rays burning resistlessly through his flesh as if it were water, shifting the cells of his body, working its slow, monstrous alchemy upon him. Peter waited until the changes were unmistakably evident in his skin and hair, and then he smashed all the mirrors in the ship. The embryos were pulsing with unnatural life, even in the suspended animation of their crystal cells. One by one he allowed them to mature, and after weeks or years destroyed the monstrosities that came from the incubators. Time went by, meaninglessly. He ate when he was hungry, slept when his driving purpose let him, and worked unceasingly, searching for the million-to-one chance. He stared sometimes through changed eyes at the tiny blue star that was Earth, wondering if the race he had left behind still burrowed in its worm-tunnels, digging deeper and deeper away from the sunlight. But after a time he ceased even to wonder. And one changeling-child he did not destroy. He fed knowledge to its eager brain, and watched it through the swift years, with a dawning hope.... * * * * * Peter closed the diary. "The rest you know, Robert," he said. "Yes," I told him. "I was that child. I am the millionth mutation you were searching for." His eyes glowed suddenly in their misshapen sockets. "You are. Your brain is as superior to mine as mine is to an anthropoid's. You solve instinctively problems that would take our mechanical computers hours of work. You are a superman."