Burke climbed into the diving suit, which had been designed for amateurs of undersea fishing to use in chilly waters. On Earth it would have been intolerably heavy, for a man moving about out of the ocean. But there was no weight here. If M-387 had a gravitational field at all, which in theory it had to have, it would be on the order of millionths of the pull of Earth. Keller sat in the control-chair, watching the instruments and the outside television screens which showed the bore now reduced to fifty feet. Somehow the more distant parts of the tunnel looked hazy, as if there were a slight mist in whatever gas had been released in it. Sandy watched Burke pull on the helmet and close the face-plate. She grasped a hand-hold, her knuckles turning white. Pam nestled comfortably in a corner of the ceiling of the control-room. Holmes frowned as Burke went into the air-lock and closed the inner door. His voice came immediately out of a speaker at the control-desk. "I'm breathing canned air from the suit," he said curtly. There were scrapings. The outer lock-door made noises. There was what seemed to be a horribly long wait. Then they heard Burke's voice again. "I've tried it," he reported. "The lighter burns when it's next to the slightly opened door. I'm opening wide now." More noises from the air-lock. "It still burns. Repeat. The lighter burns all right. The tunnel is filled with air. I'm going to crack my face-plate and see how it smells." Silence, while Sandy went white. But a moment later Burke said crisply, "It smells all right. It's lifeless and stuffy, but there's nothing in it with an odor. Hold on--I hear something!" A long minute, while the little ship floated eerily almost in contact with the walls about it. It turned slowly. Then there came brisk, brief fluting noises. They were familiar in kind. But this was a short message, of some fifteen or twenty seconds length, no more. It ended, was repeated, ended, was repeated, and went on with an effect of mechanical and parrot-like repetition. "It's good air," reported Burke. "I'm breathing normally. But it might have been stored for ages. It's stale. Do you hear what I do?" "Yes," said Sandy in a whisper to the control-room. "It's a call. It's telling us to do something. Come back inside, Joe!" They heard the outer air-lock door closing and its locking-dogs engaging. The fluting noises ceased to be audible. The inner door swung wide. Burke came into the control-room, his helmet face-plate open. He wriggled out of the diving suit. "Something picked up the fact that we'd entered. It closed a door behind us. Then it turned on lights for us. Then it let air into the entrance-lock. Now it's telling us to do something." The ship surged, ever so gently. Keller had turned on an infinitesimal trace of drive. The walls of the bore floated past on the television screens. There was mist in the air outside. It seemed to clear as the ship moved.