He started at the tip of the peninsula and zigzagged across, heading toward the isthmus. Methodically, he covered the territory, sleeping at night in the digger. On the morning of the third day, he discovered oil traces, and by that afternoon he had located the main field. He should probably have turned back at once, but now that he had found oil, he investigated more deliberately. Starting at the top, he let the image range downward below the top strata. It was the reverse of what it should have been. In the top few feet, there were plentiful fossil remains, mostly of the four species of mammals. The squirrel-like creature and the far larger grazing animal were the forest dwellers. Of the plains animals, there were only two, in size fitting neatly between the extremes of the forest dwellers. After the first few feet, which corresponded to approximately twenty thousand years, he found virtually no fossils. Not until he reached a depth which he could correlate to the Late Carboniferous age on Earth did fossils reappear. Then they were of animals appropriate to the epoch. At that depth and below, the history of Glade was quite similar to Earth's. Puzzled, he checked again in a dozen widely scattered localities. The results were always the same--fossil history for the first twenty thousand years, then none for roughly a hundred million. Beyond that, it was easy to trace the thread of biological development. In that period of approximately one hundred million years, something unique had happened to Glade. What was it? On the fifth day his investigations were interrupted by the sound of the keyed-on radio. "Marin." "Yes?" He flipped on the sending switch. "How soon can you get back?" He looked at the photo-map. "Three hours. Two if I hurry." "Make it two. Never mind the oil." "I've found oil. But what's the matter?" "You can see it better than I can describe it. We'll discuss it when you get back." * * * * * Reluctantly, Marin retracted the instruments into the digger. He turned it around and, with not too much regard for the terrain, let it roar. The treads tossed dirt high in the air. Animals fled squealing from in front of him. If the grove was small enough, he went around it, otherwise he went through and left matchsticks behind. He skidded the crawler ponderously to halt near the edge of the settlement. The center of activity was the warehouse. Pickups wheeled in and out, transferring supplies to a cleared area outside. He found Hafner in a corner of the warehouse, talking to the engineer. Hafner turned around when he came up. "Your mice have grown, Marin." Marin looked down. The robot cat lay on the floor. He knelt and examined it. The steel skeleton hadn't broken; it had been bent, badly. The tough plastic skin had been torn off and, inside, the delicate mechanism had been chewed into an unrecognizable mass.