As he hit the water at the bottom, the tube swung around the circumference of the rim to the point at its far side at which it entered its particular river. The course of his dive carried Mike to the bottom of the curve, and he started crawling up its far side to where the tunnel entered the rim-river. There the motion of the fluorescent-lighted water caught him, and he was swirled quickly to his target, twenty-five feet along, inspection plate B-36. He grabbed the hand-hold by the plate before he swirled past, loosened the plate, lifted it only enough to be sure that the room was empty, and then pushed it off, pulled himself through, and emerged into the whining dimness of Compressor Room 9, next to the machine shop. The low whine assaulting his ears was that created by the air compressors that fed the jets that drove the waters through the rim. Stepping over to the wall locker, Mike took out a dry pair of shorts, a T-shirt, and moccasins, kept there for the purpose of making changes after such swimming inspections of the rim tanks. * * * * * Before entering the machine shop, Mike spotted the Security man through the open bulkhead--just standing there while Paul and Tombu grimly worked on; and Millie sat idle, watching. Mike entered the machine shop casually, as though intent on business, brushed past the Security man, and stepped over to the tape-controlled, laser-activated milling machine as though to inspect its progress. Then, as though finding an error, he halted its operation and swung the laser-head back away from the work piece. The head swung free in his hand, attached to the machine but nevertheless free. Casually, without even looking at the Security man, he had somehow centered the laser directly on him. Just as casually, he stepped to one side. "The beam from this machine is quite capable of milling the hardest materials," he said, still casually, as though to himself. "Even a diamond can't withstand it." Now he looked directly at the Security guard. "It's capable," he said in an even tone, "of milling a hole right through your guts if you even to much as breathe too deep." Then to Chernov, "Move around behind him, out of range of this beam, and secure the man please. Millie, is there any thing in your department that will make sure he won't talk for while?" "Yes, Mike, but I don't think I'd better go there right now. There aren't many of them, but these boys seem to be spread out all over." Chernov had the gun now; and the personal communicator from the Security man as well. "O.K.," said Mike. "I don't think he can give us much trouble in there," pointing at the air-lock bulkhead through which he had just entered. "We can go in and out through the physics lab," he said. "Best we shut that off now before some more of these boys wander along."