"This is a world, Sheila! It might be a world for us, a world where Unregenerates could live, and wait!" She gasped and stared at him, and Paul Avery said: "Look at it, Falken! No one, nothing could live there." Falken said softly, "Afraid to land and see?" Yellow eyes burned into his, confused and wild. Then Avery turned jerkily away. "No. But you can't land, Falken. Look at it." Falken looked, using a powerful search-beam, probing. Vulcan was smaller even than Mercury. There was no atmosphere. Peaks like splinters of black glass bristled upward, revolving slowly in the Sun's tremendous blaze. The beam went down into the bottomless dark of the canyons. There was nothing there, but the glassy rock and the dim glints of light through it. "All the same," said Falken, "I'm going to land." If there was even a tiny chance, he couldn't let it slip. Unregeneracy was almost dead in the inhabited worlds. Paul Avery was the only recruit in months. And it was dying in the miserable outer strongholds of independence. Starvation, plague, cold, and darkness. Insecurity and danger, and the awful lost terror of humans torn from earth and light. Unless they could find a place of safety, with warmth and light and dirt to grow food in, where babies could be born and live, Gantry Hilton would soon have the whole Solar System for his toy. There were no more protests. Falken set the ship down with infinite skill on a ledge on the night side. Then he turned, feeling the blood beat in his wrists and throat. "Vac suits," he said. "There are two and a spare." They got into them, shuffled through the airlock, and stood still, the first humans on an undiscovered world. * * * * * Lead weights in their boots held them so that they could walk. Falken thrust at the rock with a steel-shod alpenstock. "It's like glass," he said. "Some unfamiliar compound, probably, fused out of raw force in the Solar disturbance that created the planets. That would explain its resistance to heat." Radio headphones carried Avery's voice back to him clearly, and Falken realized that the stuff of the planet insulated against Solar waves, which would normally have blanketed communication. "Whatever it is," said Avery, "it sucks up light. That's why it's never been seen. Only little glimmers seep through, too feeble for telescopes even on Mercury to pick up against the Sun. Its mass is too tiny for its transits to be visible, and it doesn't reflect." "A sort of dark stranger, hiding in space," said Sheila, and shivered. "Look, Eric! Isn't that a cave mouth?" Falken's heart gave a great leap of hope. There were caves on Pluto. Perhaps, in the hidden heart of this queer world.... They went toward the opening. It was surprisingly warm. Falken guessed that the black rock diffused the Sun's heat instead of stopping it.