The trail wound through the woods for a little distance and then broke into a clearing. Rick saw gear littered over the ground and pointed to it. "Looks as if they left something behind!" In a moment they were looking through what was evidently Ko's entire luggage. Sing kicked at a pile of cooking utensils. "They took the mules but left everything else." "Funny they'd do that," Rick said thoughtfully. "After all, Ko was the boss. He must have arranged the ambush. Unless we're wrong about him." "I don't think we're wrong," Scotty denied. "You hit it on the nose when you said a man doesn't pull the pin on a grenade unless he's ready to toss it. Ko must be the boss." Sing examined a richly embroidered robe. "My guess is that Ko hired a few Tibetan bandits. They wouldn't worry about him or his belongings after being met by heavy resistance. And his bearers would be afraid to stay and face him. Or maybe they thought he was killed while attacking us. There was a lot of noise, and it was dark." Rick thought Sing was probably right. He walked over to a pile of furs. "What are these?" he asked. "Ko must have been a fur trader." Sing looked up. "Water bags. Goatskin. Very common in China." He dropped the robe and came to look, his face wrinkling into a frown. "But usually a man doesn't carry so many. Very funny." Rick and Scotty examined one with interest. It was a whole skin, except for head and feet. Even the tail was still attached. The ends of the legs had been sewed up, but the neck was left open. Attached to the neck opening was a rawhide thong that could be used to bind the opening tight when the skin was filled with water. "These are good bags," Sing said. "Better than most." "Perhaps he planned to sell them," Rick suggested. "Don't think so." The Chinese guide shook his head. "People here make their own. Every time they kill a goat for meat, that's a new goatskin. The Buddhist Tibetans, who don't kill anything, even flies, use pottery jugs." Scotty had started counting the bags. He paused at the ninth and held it up. "This one is split open. Looks like the seam gave way. There's a sort of funny lining." Rick took the skin and turned it inside out. It was smooth and glassy on the inside, and the substance was completely transparent because he could see the skin underneath. Sing felt of it. "Never saw anything like that before." Rick held it to his nose and sniffed. It was odorless. He took his pocketknife and scraped at it while the others watched. A tiny flake shaved off. He tested it between his fingers, and it was flexible as rubber. An idea was growing in his head. "It's crazy," he said. "But you know what I think this is? I think it's plastic!" "The professor can tell us," Scotty suggested. "Come on. Let's take it to him." They ran back up the trail, Rick leading with the skin. If the stuff were plastic, it could mean only one thing. He lengthened his stride.