"I said God cared," answered Alemán quietly, "not that He will do our work for us." "Stow the theology, you two," said Catherine. "We're going to pieces in here. Can't somebody start a song?" Alemán nodded. "Who has a guitar?" When there was no response, he began singing a capella: "_La cucaracha, la cucaracha, Ya no quiere caminar--_" Voices joined in, self-consciously. They found themselves too few, and the song died. Catherine rubbed her fingers together. "Even my pockets are cold now," she said wryly. Gilchrist surprised himself; he took her hands in his. "That may help," he said. "Why, thank you, Sir Galahad," she laughed. "You--Oh. Hey, there!" O'Mallory, off guard detail now that everyone was assembled here, came over. He looked even bulkier than before in half a dozen layers of clothing. Gilchrist, who had been prepared to stand impotently in the background while the engineer distributed blarney, was almost relieved to see the fear on him. _He_ knew! "Any word?" asked Catherine. "Not yet," he muttered. "Why 'ave we so leetle light?" inquired Alemán. "What is it that draws the current so much? Surely not the heaters." "No. It's the pump. The air-intake pump down in the pile room." O'Mallory's voice grew higher. "It's working overtime, sucking in more hydrogen. Don't ask me why! I don't know! Nobody does!" "Wait," said Catherine eagerly. "If the room's losing its warm gas, and having to replace it from the cold stuff outside, would that account for the trouble we're having?" "No," said O'Mallory dully. "We can't figure out where the hydrogen's disappearing to, and anyway it shouldn't make that much difference. The energy output down there's about what it's supposed to be, you know." Gilchrist stood trying to think. His brain felt gelid. But damn it, damn it, damn it, there must be a rational answer. He couldn't believe they had blundered into an ugly unknown facet of the cosmos. Natural law was the same, here or in the farthest galaxy--it had to be. Item, he thought wearily. The pile was operating as usual, except that somehow hydrogen was being lost abnormally fast and therefore the pump had to bring in more from Triton's air. But-- --Item. That couldn't be due to a leak in the heating pipes, because they were still at their ordinary pressure. --Item. The gas in the pipes included some radioactive isotope. Nevertheless-- --Item. It could not be hydrogen-3, because the pile was working normally and its neutron leakage just wasn't enough to produce that much. Therefore, some other element was involved. Carbon? There was a little methane vapor in Triton's atmosphere. But not enough. Anyway, carbon-13 was a stable isotope, and the pile-room conditions wouldn't produce carbon-14. Unless-- _Wait a minute!_ Something flickered on the edge of awareness. Danton had buttonholed O'Mallory. "We were talking about using the battery banks," he said.