"There was a good two hours of climbing ahead of us. We'd have been dead a long time before we got there." "Okay," Brace said. "Let's go wreck these radio posts." "I'm afraid he has that all figured out," Harvey said sadly. "You notice the posts shut you off when you're going one way, and turn you on again when you're going back. If you go over there and wreck them, there'll be nothing to turn you on again." Red cursed long and loud. "There must be _some_ way to beat this oxygen racket." "We'll think of something," Harvey said determinedly. But the echo of his confident words rapidly faded as they moved through the grain fields. He was tired and chilled. Think of something? That white-haired devil in that eagle's nest had been thinking of the same subject for a decade. Could there be any angles he had overlooked? * * * * * Long after Ruth was asleep that night, Harvey lay in bed thinking. He reviewed, item by item, everything he could remember about electricity, radiation, the laws of gases, atmospheric constituents, the mechanics of partial pressures--all the tag-end memories of his college science courses. He felt that if there was a solution, it had to be something elementary, something that matched the simplicity of Baker's own idea. The thoughts went around and around in his brain, an intricate and dizzying dance, forming a pattern that grew fuzzier and fuzzier and fuzzier.... He sat up with a start. His brain was tingling with something ... something that seemed to be.... He struggled into his clothes, and dashed out of the house. He ran up the dark road and burst into Dr. Lurie's house. "Doc, Doc, wake up!" he yelled. "I need some scientific advice!" Shortly after sunrise, when most of the settlers were heading for the fields, Harvey and Dr. Lurie went to the COM booth. "Better let me do the talking," Harvey said. "I'd prefer it that way," Dr. Lurie said. * * * * * Baker, sitting before the electronic telescope, was enjoying the sight of the great phalanx of settlers swarming into the fields, when the buzzer sounded on his communication set. In a moment, two faces appeared--Dr. Lurie and Harvey Flanders. They weren't wearing their oxygen packs. "Good morning, gentlemen," Baker said affably. "Hiya," said Harvey Flanders. "Well!" said Baker. "I'm certainly glad to see you in such good spirits after last night's expedition." "Thanks," Harvey said. "All we want to tell you is that you don't have to send us any oxygen any more." Baker chuckled. "I see. You are going on strike, eh?" "No," Harvey said, "we're going to keep working--but for ourselves, not for you, Colonel. You see, Dr. Lurie here has put his scientific brain to work and come up with a substitute for your oxygen pack." "How incredible," Baker said pleasantly. "And what is the substitute, if I may ask? Alcohol?"