He stepped up behind the physicist in the pitch blackness, and judging carefully, brought his fist down on the nape of the man's neck in a hard rabbit punch. Konrad Bern dropped unconscious to the floor of the tube. Then MacHeath let his chest pump air into his lungs in long, harsh gasps. Shakily, he lowered himself to the floor beside Bern and squatted on his haunches, waiting for the hiss of the bleeder valve that would tell him that the air pressure had been raised to allow someone to enter the air lock. It was Morgan, the FBI man, who finally cracked the door. Griffin and Dr. Kent were with him. "You all right?" asked Morgan. "I'm fine," MacHeath said, "but Bern is going to have a sore neck for a while. I didn't hit him hard enough to break it, but he'll get plenty of sleep before he wakes up." More FBI men came in, and they dragged out the unprotesting Bern. Dr. Kent said: "Well, I'm glad that's over. I'll have to get back and see what Dr. Nordred is raving about." "Raving?" asked MacHeath innocently. "Yes. While I was in the pump room reducing the pressure, he called me on the interphone. Said he'd been looking all over for me. He and Luvochek and Bessermann are up in the lab." He frowned. "They claim that one of the radiolead samples was floating in the air in the lab. It's settled down now, I gather, but it only weighs a fraction of what it should, though it's gaining all the time. And that's ridiculous. It's not at all what Dr. Nordred's theory predicted." Then he clamped his lips together, thinking perhaps he had talked too much. "Interesting," said MacHeath blandly. "Very interesting." * * * * * Senator Gonzales sat in Brian Taggert's sixth-floor office in the S.M.M.R. building and looked puzzled. "All right, I grant you that Bern couldn't have been the saboteur. Then why arrest him?" Dave MacHeath took a drag from his cigarette before he answered. "We had to have a patsy--someone to put the blame on. No one really believed that it was just bad luck, but they'll all accept the idea that Bern was a saboteur." "We would have had to arrest him eventually, anyway," said Brian Taggert. "Give me a quick run-down," Gonzales said. "I've got to explain this to the President." "Did you ever hear of the Pauli Effect?" MacHeath asked. "Something about the number of electrons that--" "No," MacHeath said quickly. "That's the Pauli _principle_, better known as the Exclusion Principle. The Pauli _Effect_ is a different thing entirely, a psionic effect. "It used to be said that a theoretical physicist was judged by his inability to handle research apparatus; the clumsier he was in research, the better he was with theory. But Wolfgang Pauli was a lot more than clumsy. Apparatus would break, topple over, go to pieces, or burn up if Pauli just walked into the room.