"It's nearer the base, sir. No more than three hours' travel, if that much. We could make it on one tank of air apiece, sir, and have the extra one for margin. We could make it to base from there, sir, if we were there. But we're not, and it's three hours' travel from here! We'd get there...." "You _would_ get there?" demanded McCauley ominously. "Or you _will_ get there?" "_Will_, sir." But the young officer's voice was bewildered. "For your information," said McCauley curtly, "the Repeater One relay unit is exactly like the relay unit at Repeater Two. I may add that it is in bright sunshine, but will not be so indefinitely."--This was because McCauley remembered an air tank which had lain in shadow until its metal shivered brittlely when struck and the air inside it was a liquid. "It was carried to its position and mounted exactly as the relay for Repeater Two was. Now figure it out for yourself! If you still don't understand when you get to it, call me from there. Now get moving! Sunset's not far away." He clicked off his microphone, but left the receiving unit on. The relay at Repeater Two would pick up suit-radio speech and relay it back, the pickup being from its all-direction antennae. McCauley heard mumblings. Then, very distinctly, Holmes spoke. "Understand, I'm going to cooperate with you, getting to Repeater One, but that doesn't mean I like you any better!" Kent said resentfully: "I figured you'd have to fight me for the air to get back with. And you pulled the same trick on me! But we'll manage eventually...." More mutterings. Then: "Cripes! Let's get going!" There were those peculiar noises which a microphone inside a space suit picks up and transmits. Breathings. Clankings. Sometimes the squeak of metal sliding on metal. McCauley listened. Presently the noises faded and ceased. The two young space-suited officers had descended the mountain to where they were not in line of sight of the relay, and consequently it could not pick up their suit-radio communications to relay back to McCauley. The communications officer tapped on the office door. "We're through to Farside Base, sir," he reported. "The relay system's working splendidly. Farside just asked for an Earth Relay link to Lunar Base." "Give it to 'em," said McCauley succinctly. He waited, listening. He had Repeater One as well as Two set so it would retransmit any local pickup on helmet-phone frequency, but it was half an hour before anything but the peculiar singing murmurs of empty space came from the loud-speaker. Then he heard heavy breathing.