With half of his mind he made tests. There was atmosphere, almost pure chlorine. Nor was it unduly cold. An electroscope gave him the answer. Pluto was a radioactive planet, warmed from within by the powerful radiations of the ore. Duncan took the dead Olcott’s helmet and adjusted it upon himself. Turning on the power made the intertron knob glow, but there was no other result. The Varra, of course, could not safely venture within the Heaviside Layer of any planet, and Pluto had a Layer, since it had an atmosphere. Chlorine—radium—Duncan shook his head, trying to fit the puzzle together. There were no Plutonians. Why, then, had the Varra fostered the legend of the mind-vampires? Creatures composed of pure energy could not exist on a radioactive planet; the radiations would be fatal to their complicated electronic structures. Duncan thought for a long time. At last he had the answer, so astoundingly simple that he found it difficult to believe. But it checked. And that meant— He rose and went slowly to where Andrea’s body lay, still in the spacesuit, her face composed and lovely in death. Duncan’s lips twisted. He knelt. “Andrea—” She was trying to tell him something, he thought. What? “Tell Earth what I’ve found out? Is that it?” He hesitated. “It’s no use. We’re forty thousand million miles from the Sun. The radio won’t carry that far, even if it’d get through the Heaviside Layer on Pluto. There’s no way to send a message back.” There was no way. Nor could the cruiser retrace its course. There was not enough fuel left. The jets would be exhausted before Saturn’s orbit was reached, and the speed would increase as the ship plunged Sunward, increase to a point where deceleration would be impossible. “There’s no way, Andrea. I can’t send the message—” Duncan stopped. There was a way, after all, though it meant death. * * * * * He seated himself before the radio-recorder and adjusted it to automatic-repeat. His message would be imprinted on metal wire-tape, and continue to be sent out into the void till the ship itself was destroyed. Duncan pulled the microphone toward him. His voice was coldly emotionless. “CQX. CQX. Recorded on Pluto. All ships copy. Relay to proper authorities. Pluto is uninhabited. Its atmosphere is pure chlorine. No life-form known to science can exist in a chlorine atmosphere or on a radioactive world. The Plutonian mind-vampires do not exist. The legend was created by the Varra for their own purposes. The actual mind-vampires are the Varra themselves.” Now it would be theorizing, but Duncan was certain that his guess was correct.