They returned to the room of the spaceships, seeking one of the small, portable radio-amplifiers used for searching out radium. It was known as a "squeaker" because of the constant din it made while in use; the noise would cease only when radium was within a hundred feet of the mechanism. He found one after searching a few of the smaller ships. With the portable radio strapped to his back, power switched on, he started again down the main tunnel. The globes set up their seductive rhythms as before, but he could not hear them above the discord of his squeaker. Failing to lure him as before, they sought to force him in the direction they desired him to go by darting at him suddenly, lashing him with their tentacles. But it was a simple thing to elude them. Still remained the question: why could they want to lure him into that stinking pool of acid? He flashed a beam of heat at the nearest of the annoying globes. Under the released energy it glowed, yet did not melt. But the tentacles sheared off and the blue lights faded. The flow of music changed to shrill whines as of pain and its rolling ceased. The others drew back; he turned down another tunnel. They stopped at the cave beyond the one where he had found the robot-girl. It was sealed by a locked door, one of the airlock-doors from that space vessel, firmly cemented into the natural opening of the cave. Nat bent forward, listening, his helmeted head pressed against the door. No sound. He was suddenly aware of the dead silence that pressed in on him from all sides now that the globes no longer sang and his "squeaker" had been turned off. The powerful energy of his heat-beam sputtered as it melted the lock into incandescent droplets which sizzled as they trickled down the cold metal of the door. The greasy, quartz-like material at the side of the door glowed in the heat from his rod, but no visible effect upon it could be seen. What was that material? He knew, yes, he knew--but he could not place a mental finger on it. He thrust the shoulder of his good arm against the heavy door, swung it inwards, stepped inside. The light of his torch pierced the silence, picked out a human skeleton in one corner. He hurried toward it--no, it was not entirely a skeleton as yet. The flesh and bone had been eaten away from the lower part of the body to halfway up the hips, as though from some strong acid. The rest of the large, sturdy frame lay sunken under the remains of a spacesuit which was tied clumsily around the middle to retain all the air possible in the upper half of it. Evidently some acid had eaten away the lower half of the man's body after he had suffocated. The face was that of a Norwegian.