"Your guess is as good as mine, Troubles," Perry returned, awedly. "But we must be at the final center of things--at the place the robots up there were meant to guard. Whatever that may be." They rested several minutes, not saying much. Then Troubles arose shakily. "Come on. Let's explore, fella," she urged. Perry supported her unsteady steps as they walked out of the open-ended chamber. The ground around them was covered with a kind of coarse, shaggy moss. Trees, formed like oversized bushes, reared up over them, bearing strange fruits. The light which came from above, was warm, like sunshine. "Kind of like a heaven here, isn't it?" the girl asked. Perry grinned, though his head still ached. "What are you trying to do, pull my leg?--talking that kind of bunk!" he growled. "Only it's so still and deserted-looking," Lyssa went on. "There's not a path anywhere. And look! That building!" They had passed through a grove. Near them was a long structure of white stone. But it was like a ruin. Its rows of windows, with their carved decorations, some of them human figures, were sightless and empty, except for intruding masses of coarse, vinelike plants. Once, from its appearance, the building might have been a gigantic apartment house, teeming with inhabitants. And there were others like it, near, and far off on the high slopes of the cavern. But all had that same tenantless aspect. * * * * * Perry and Troubles were moving along a street of what might have been a village. At the farther end of the street was a domed edifice of glass of different colors. And at the crest of the dome, standing firmly on a stubby cylinder which was evidently meant to represent some sort of ship, was the golden figure of a man, clad in flowing robes. The face of the colossus was stern and kindly as he stared off into the distance as if somewhere there he watched for the realization of a hope. The great staff he clutched, rested on his pedestal and rose straight upward to join with the roof of the cavern, above. There was a steep stairway leading down to the sunken grounds of the domed edifice. Lyssa, hurrying ahead on still unsteady legs, and looking up too intently at the golden image above, lost her balance and pitched forward on the steep slant. She tumbled the full length of it. Perry gave a shout of concern and leaped after her, sure that she must have at least broken some bones. But she got up quite nimbly and promptly. "Stumble bum!" she muttered, frowning. And then in a new and different kind of tone: "Perry--that was funny, wasn't it? I'm not hurt at all!" There was wonder in her dark eyes. He was puffing with relief, but was startled, too. "Yeah, I see!" he said. "It's stranger than the desertion, here. I landed light myself. It was as though the air was holding me back--partly. As though it has a higher resistance, or something! But that's looney!"