It was a new world, all by itself; or else it was a tomb. And there was one other change, one that you couldn't see from the outside. The solid meters of lead in its outer skin, the shielding to keep out cosmic rays, were gone. A man had just finished engraving the final stroke on its nameplate, to the left of the airlock--_The Avenger_. He stepped away now, and joined the group a little distance away, silently waiting. Lorelei said, "You can't do it. I won't let you! Peter--" "Darling," he began wearily. "Don't throw your life away! Give us time--there must be another way." "There's no other way," Peter said. He gripped her arms tightly, as if he could compel her to understand by the sheer pressure of his fingers. "Darling, listen to me. We've tried everything. We've gone underground, but that's only delaying the end. _They_ still come down here, only not as many. The mortality rate is up, the suicide rate is up, the birth rate is down, in spite of anything we can do. You've seen the figures: we're riding a curve that ends in extinction fifty years from now. "They'll live, and we'll die, because they're a superior race. We're a million years too far back even to understand what they are or where they came from. Besides them, we're apes. There's only one answer." She was crying now, silently, with great racking sobs that shook her slender body. But he went remorselessly on. "Out there, in space, the cosmics change unshielded life. They make tentacles out of arms; or scales out of hair; or twelve toes, or a dozen ears--or a better brain. Out of those millions of possible mutations, there's one that will save the human race. We can't fight _them_, but a superman could. That's our only chance. Lorelei--darling--don't you see that?" She choked, "But why can't you take me along?" He stared unseeingly past her wet, upturned face. "You know why," he said bitterly. "Those rays are strong. They don't only work on embryos; they change adult life forms, too. I have one chance in seven of staying alive. You'd have one chance in a million of staying beautiful. I couldn't stand that. I'd kill myself, and then humanity would die, too. You'd be their murderer." Her sobs gradually died away. She straightened slowly until he no longer had to support her, but all the vitality and resilience was gone out of her body. "All right," she said in a lifeless voice. "You'll come back, Peter." He turned away suddenly, not trusting himself to kiss her goodbye. A line from an old film kept echoing through his head. "_They'll_ come back--but not as _boys_!" We'll come back, but not as men. We'll come back, but not as elephants. We'll come back, but not as octopi. * * * * *