Off gloom, and cold, and the domes turned to blocks of ice, and a final night gaping before all men. Off the chasm of loneliness between the Hill and the Earth. They were back in the chemical section when Alemán came out of his lab. The little man's olive skin had turned a dirty gray. "What is it?" Gilchrist stopped, and something knotted hard in his guts. "_Madre de Díos--_" Alemán licked sandy lips. "We are finished." "It's not that bad," said Catherine. "You do not understand!" he shrieked. "Come here!" They followed him into his laboratory. He mumbled words about having checked a hunch, but it was his hands they watched. Those picked up a Geiger counter and brought it over to a wall and traced the path of a buried heating pipe. The clicking roared out. * * * * * "Beta emission," said Gilchrist. His mouth felt cottony. "How intense?" whispered Catherine. Gilchrist set up an integrating counter and let it run for a while. "Low," he said. "But the dosage is cumulative. A week of this, and we'll begin to show the effects. A month, and we're dead." "There's always some small beta emission from the pipes," said the girl. "A little tritium gets formed down in the pile room. It's ... never been enough to matter." "Somehow, the pile's beginning to make more H-3, then." Gilchrist sat down on a bench and stared blankly at the floor. "The laws of nature--" Alemán had calmed down a bit, but his eyes were rimmed with white. "Yes?" asked Catherine when he stopped. She spoke mostly to fend off the silence. "I 'ave sometimes thought ... what we know in science is so leetle. It may be the whole universe, it has been in a ... a most improbable state for the past few billion years." Alemán met her gaze as if pleading to be called a liar. "It may be that what we thought to be the laws of nature, those were only a leetle statistical fluctuation." "And now we're going back onto the probability curve?" muttered Gilchrist. He shook himself. "No, damn it. I won't accept that till I must. There's got to be some rational explanation." "Leakage in the pipes?" ventured Catherine. "We'd know that. Nor does it account for the radiation. No, it's--" His voice twisted up on him, and he groped out a cigaret. "It's something natural." "What is natural?" said Alemán. "How do we know, leetle creeping things as we are, living only by the grace of God? We 'ave come one long way from home." His vision strayed to the viewport with a kind of horror.