Norden bent, picked up the little cage and swung towards the door. He took one step forward, stopped abruptly, and bent again. His hand gripped the collar of the thing on the floor and, straightening, he heaved it up against the light gravity of the Moon. The thing sailed across the laboratory, heading toward the rear of the heavy protogravity generator. Norden cushioned the cage of lizards against his chest and dropped to the floor in the shelter of the computer. There was a blast that nearly ruptured his eardrums and the accompanying glare of greenish-yellow light burned through his eyelids into his brain. The floor heaved and shook, while sections of the curved roof began falling. The air gushed upwards, and the floor jarred again as the automatic airseal dropped, cutting off other sections. Norden jumped toward a plainly marked closet, and threw it open. He yanked down one of the spacesuits stored there for emergency purposes, thrust the lizard cage inside, closed it, and turned on the oxygen. Adapted to the thin air of Mars, it seemed likely the animals would remain alive. He groped about until he located another suit that would fit, cursed as he found it zippered closed, and finally worked it open. Once in, he sealed it, and headed toward the personnel lock on the big emergency airseal. He got through just as the guards were about to enter in their own spacesuits, dragging rescue equipment. Miles was with them, waiting impatiently while Norden slipped his helmet off. "Who was it?" he demanded. "Armsworth," Norden told him. "After he passed the fluoroscope test!" Miles sighed, but there was no surprise. "Damn! I should have had him checked when he came back from inspecting the other side. They must have had a spy all ready to make the switch as soon as they got him. Or maybe the test doesn't mean anything." The guards had come back. One of them began to report on what they had seen. Most of the damage had been confined to the roof of the building, and to the big protogravity generator, which apparently had shielded the rest of the equipment. Norden and Pat, who had finally been called, went inside in their suits to supervise clearing away the debris. Outside, a crew was already erecting a new roof on the laboratory, using prefab sheets. Aside from the generator they had never used, nothing irreplaceable had been hurt. And the two little male lizards were doing well enough. Inside of two hours the laboratory was back in full operation. By common consent, Pat and Norden abandoned all idea of sleeping. Norden started to draw up a list of new tests, and then went back to the potassium shield. It seemed to produce a very slight quantitative difference in the reaction of the females. He consulted the vague speculations in his own works on possible other spectra, and came back.