Hargraves heard the voices, saw the conclusion they were reaching. "One moment," he said. The voices went into silence. Eyes turned questioningly to him. "Even if these men are really Hal Sarkoff and Eddie Nevins and Sam Reese, if they are the companions we knew as dead who have miraculously been returned to us, there are still facts that do not fit into a logical pattern. Even here on this world the laws of logic must hold true." Silence fell. Men looked at him and at each other. Where there had been wonder on their faces, new doubts were appearing. "What facts, Jed?" Sarkoff questioned. "The sphere that attacked us, that attempted to destroy us, without warning. This is a fact that does not fit." "The sphere?" Uncertainty showed on Sarkoff's face. Then he grinned again and turned to Thulon. "You tell him about that sphere." "Gladly," Thulon's thoughts came. "As you know, Vega has two planets. Long ago we were at war with the inhabitants of this other planet. Part of our defenses around our own planet were floating fortresses. The war is done but we have left guards in the sky to protect us if we are attacked. The sphere that attacked you was one of our automatic forts which we had left in the sky." "Ah!" said Hargraves. The cold logic of his mind sought a pattern that would include fortresses in the sky. Presuming war between two planets, such fortresses were logical. But-- "The construction of such a sphere indicates vast technical knowledge, tremendous workshops. I have seen no laboratories and no industrial centers that could produce such a fortress. I have, moreover, seen no civilization that will serve as a background for such construction." * * * * * He waited for an answer. Usher, the archeologist, looked suddenly at him, then looked at Thulon. "The fortresses were built long ago," Thulon said. "In those past milleniums we had industrial centers. We no longer need them and we no longer have them." "Then there _is_ another stage!" the archeologist gasped. "You are past the city stage in your evolutionary process. You are beyond the metal age. What--" Usher eagerly asked. "What comes after that?"