The Earthmen tried to obey. Like automatons they ran, their eyes fixed and staring, while the clamor of pursuit grew louder. Looking back, Garth saw a flash of shining movement The Zarno! "Faster!" There were no side tunnels. They came out into a small cave, completely empty. It was a cul-de-sac. Light was reflected brightly from three walls. The fourth wall was dead black--neither rock nor stone. It was like a jet curtain, blocking their path. Garth jerked to a halt, knowing the utter hopelessness of futility. They were trapped now. The Zarno were pursuing, unmistakably. Garth took out his useless gun. His face was set in grim lines. What good were bullets against the silicate creatures? But waiting helplessly was far worse. At least he could try to fight. He had forgotten to command his charges to halt. Glancing around, Garth saw something that made his eyes widen in incredulous amazement. Paula was walking toward the black curtain--the wall-- She stepped through it and vanished. Brown followed her. Then another man. And another. Last of all, Sampson, disappearing like a ghost through the blackness! Heavy footsteps whirled Garth about. Down the corridor he could see the flashing gleams that heralded the Zarno. His tight grin was a grimace. "The hell with you, pals," he said softly--and turned again. He raced in pursuit of the others. Leaped through the dark curtain! * * * * * There was an instant of grinding, jolting shock that left him blind. He staggered, caught himself, and saw that he was in a passage that led toward a distant brightness. Silhouetted against the glow were the moving figures of his companions. He sprinted after them. But he did not overtake them till they had emerged in a cavern unlike any he had seen before. "Okay! Stop! Stop, that's right." They halted, motionless. Garth looked behind him, but there was no trace of the Zarno. This cavern was lighted like the others. But there were fewer machines. Row after row of the giant four-armed robots stood like an army on the dark-metal floor. The walls were jeweled, thousands of pearly disks studding them. A low humming came from a machine nearby, a tripod with lenses surmounting a square box. Garth walked through it. He hesitated, glanced around again, and then peered through the lenses. A voice seemed to speak within his brain. "--invoked the rule of silence. After that, Genjaro Lo declared that space travel was inevitable and might solve the natural problems of our civilization--" It had spoken in the Ancient Tongue. And, at the same time, Garth had seen a picture of a huge, four-armed being with a bulging, yet oddly symmetrical head, standing on a rostrum addressing a multitude-- "_Ed!_" The voice rang through the silent cavern. "Ed Garth! You made it!"