Peetn disengaged his tentacle-tip and strode off down the slope to the subterranean entrance of the pump room. Clark hesitated a moment and then followed, more slowly because of his wasted strength, Peetn turned and waited for him at the head of the steps, and they entered the cavern together. Clark could not see for a few minutes in the gloom, and he stood still, while Peetn, with his more adaptable sight organs, moved about with ease in the familiar surroundings. The multiple noises which rebounded in the enclosed space beat through the Earthman's open faceplate, betraying the secret of the darkly looming masses. "Machinery," he said softly. Peetn went through his customary routine, conscious of the stranger's eyes watching his every move, and conscious also of a pitying wonder in them. They quit the underground room, Peetn gently tugging Clark away from the four gauges which measured the water-flow through the monster pipes, and entered the valve-house. Peetn's tentacles caressed the valve-wheels and giant housings reverently--and uselessly--while the stranger once again watched with interest. Peetn was suddenly startled by a gusty, explosive sound from the alien. "What a hell of a mechanic you are!" laughed the Earthman. "I don't believe you know the first thing about all this, and yet you're obviously the caretaker around here. The pumps down there are in a bad way. Why don't you oil them?" Peetn stuck out his tentacle and they shook hands. "Yeah, we're pals, but I still think you're a bust. Look," he walked over to one of the valve wheels and grasped it by the rim, "there's hardly a trickle going through the pipes. Why don't you open her up, like this--" The valve creaked protestingly and moved a fraction of an inch under the Earthman's effort. Gauges on the wall quivered slightly and advanced an imperceptible amount along their calibrated scales. Peetn went suddenly berserk. He lashed out with his tentacles and caught Harrison Clark's straining figure about the waist, flinging him across the narrow room with a metallic clangor. He stood over the cowering figure, his tentacles poised threateningly. This creature was meddling with the machinery! "Hey, wait a minute!" shouted the shaken Earthman, raising himself on an elbow and looking up into the inscrutable face of the Martian. "I'm not trying to hurt anything! Sorry if I've done anything wrong. Here, shake hands!" He extended his hand and reluctantly the Martian took it. They went back to the little hollow, Clark limping a bit from his fall. Peetn enclosed himself in a shell of reticence after the episode in the valve-house, and it was only by dint of hard labor that the Earthman was able to coax him out of it. * * * * *