At the foot of the ramp was a vast, low cavern, stretching out of sight in all directions. It was dim, shading into the darkness of distance. Its floor was water, flat water, subdivided into large rectangular vats. In most of the vats vegetation grew in various stages, greening under the ultraviolet rays that radiated from the low roof. Between the vats ran straight, narrow walkways of packed earth. Happy waddled along one of the walkways until he found an empty vat. He lowered himself over its edge and sank happily into the still, cool water, like a hippopotamus submerging. He immersed himself completely, then lay back in the water, with only his face floating barely above the surface. Shadow appeared, apparently out of nowhere, and sat down on the edge of the vat, letting his flat legs dangle into the water. "Nothing like it," proclaimed Happy, splashing a little. "Nothing on Mars like it. You ought to come on in, Shadow. As flat as you are, you ought to float on the surface without any trouble at all." Shadow nodded silently, but made no move. "I don't see why the Toughs can't take care of their own barracks," complained Happy, returning to the subject closest to his displeasure. "You reckon the Toughs are actually the rebels, and the Masters can't make them do anything?" Shadow shook his head, but whether in negation or disclaimer of knowledge, Happy could not interpret. Happy flinched, and shifted in the vat. "There's still part of a skeleton in here," he announced. "I thought this was an empty one." Moving, he flinched again. With purpose, he aroused himself and ploughed to the edge of the vat. "I've got to find another vat," he said. "I can't take a nap if I'm going to get punched in the fanny with bones every five minutes." He heaved himself over the edge onto the walkway with difficulty, and got slowly to his feet. Shadow lifted his feet out of the vat, stood up and vanished. Happy knew how Shadow was able to disappear so suddenly, and it did not disturb him. Seen directly from front or rear, Shadow had the dimensions of a normal, black-skinned man. But Shadow was flat, no thicker than half an inch. When Shadow turned sidewise, he vanished to the sight. Occasionally, Happy wondered how Shadow happened to be, and why he was here in the caverns, but it was not the sort of thing to bother his mind for very long. Happy moved along the walkways, peering into the vats which appeared to be empty. He assumed Shadow was following him; Shadow always did. Around corners, he came upon blubbery creatures like himself, tending the plants. They nodded greeting at him, and Happy nodded back. His search was discouraging. All the vats not filled with plants seemed to have corpses in them, in varying stages of decomposition.