That was all he needed to know. For the first time Alvin dared to turn his mind upon the only plan that offered any hope. He was far too stubborn to accept either of the alternatives Seranis had offered him, and even if there had been nothing at stake he would have bitterly resisted any attempt to override his will.

             In a little while Seranis would return. He could do nothing until they were in the open again, and even then Seranis would be able to control his actions if he attempted to run away. And apart from that, he was sure that many of the villagers could intercept him long before he reached safety.

             Very carefully, checking every detail, he traced out the only road that could lead him back to Diaspar on the terms he wished.

             Theon warned him when Seranis was near, and he quickly turned his thoughts into harmless channels. It had never been easy for her to understand his mind, and now it seemed to Seranis as if she were far out in space, looking down upon a world veiled with impenetrable clouds. Sometimes there would be a rift in the covering, and for an instant she could catch a glimpse of what lay beneath. She wondered what Alvin was trying to hide from her. For a moment she dipped into her son's mind, but Theon knew nothing of the other's plans. She thought again of the precautions she had taken: as a man may flex his muscles before some great exertion, she ran through the compulsion patterns she might have to use. But there was no trace of her preoccupation as she smiled at Alvin from the doorway.

             "Well," she asked, "have you made up your mind?"

             Alvin's reply seemed frank enough.

             "Yes," he said. "I will return to Diaspar."

             "I'm sorry, and I know that Theon will miss you. But perhaps it's best: this is not your world and you must think of your own people."

             With a gesture of supreme confidence, she stood aside to let Alvin pass through the door.

             "The men who can obliterate your memory of Lys are waiting for you: we expected this decision."

             Alvin was glad to see that Seranis was leading him in the direction he wished to go. She did not look back to see if he was following. Her every movement told him: "Try and run away if you like—my mind is more powerful than yours." And he knew that it was perfectly true.

             They were clear of the houses when he stopped and turned to his friend.

             "Good-bye, Theon," he said, holding out his hands. "Thank you for all you've done. One day I'll be back."

             Seranis had stopped and was watching him intently. He smiled at her even while he measured the tu^enty feet of ground between them.

             "I know that you're doing this against your will," he said, "and I don't blame you for it. I don't like what I'm doing, either." (That was not true, he thought. Already he was beginning to enjoy himself.) He glanced quickly around: no one was approaching and Seranis had not moved. She was still watching him, probably trying to probe into his mind. He talked quickly to prevent even the outlines of his plan from shaping among his thoughts.

             "I do not believe you are right," he said, so unconscious of his intellectual arrogance that Seranis could not resist a smile. "It's wrong for Lys and Diaspar to remain apart forever: one day they may need each other desperately. So I am going home with all that I have learned— and I do not think that you can stop me. "

             He waited no longer, and it was just as well. Seranis never moved, but instantly he felt his body slipping from his control. The power that had brushed aside his own will was even greater than he had expected, and he realized that many hidden minds must be aiding Seranis. Helplessly he began to walk back toward the center of the village, and for an awful moment he thought his plans had failed.

             Then there came a flash of steel and crystal, and the metal arms closed swiftly around him. His body fought against them, as he had known it must do, but his struggles were useless. The ground fell away beneath him and he caught a glimpse of Theon, frozen by surprise with a foolish smile upon his face.

             The robot was carrying him a dozen feet above the ground, much faster than a man could run. It took Seranis only a moment to understand his ruse, and his struggles died away as she relaxed her control. But she was not defeated yet, and presently there happened that which Alvin had feared and done his best to counteract.

             There were now two separate entities fighting inside his mind, and one of them was pleading with the robot, begging it to set him down again. The real Alvin waited, breathlessly, resisting only a little against forces he knew he could not hope to fight. He had gambled: there was no way of telling beforehand if the machine could understand orders as complex as those he had given it. Under no circumstances, he had told the robot, must it obey any further commands of his until he was safely inside Diaspar. Those were the orders. If they were obeyed, Alvin had placed his fate beyond the reach of human interference.

             Never hesitating, the machine raced on along the path he had so carefully mapped out for it. A part of him was still pleading angrily to be released, but he knew now that he was safe. And presently Seranis understood that too, for the forces inside his brain ceased to war with one another. Once more he was at peace, as ages ago an earlier wanderer had been when, lashed to the mast of his ship, he had heard the song of the Sirens die away across the wine-dark sea.

10.

             "So you see," concluded Alvin, "it will carry out any orders I give, no matter how complicated they are. But as soon as I ask questions about its origin, it simply freezes like that."

             The machine was hanging motionless above the Master Associa-tor, its crystal lenses glittering in the silver light like a cluster of jewels. Of all the robots which Rorden had ever met, this was by far the most baffling: he was now almost sure that it had been built by no human civilization. With such eternal servants it was not surprising that the Master's personality had survived the ages.

             Alvin's return had raised so many problems that Rorden was almost afraid to think of them. He himself had not found it easy to accept the existence of Lys, with all its implications, and he wondered how Diaspar would react to the new knowledge. Probably the city's immense inertia would cushion the shock: it might well be years before all of its inhabitants fully appreciated the fact that they were no longer alone on Earth.

             But if Alvin had his way, things would move much more quickly than that. There were times when Rorden regretted the failure of Seranis' plans—everything would have been so much simpler. The problem was immense, and for the second occasion in his life Rorden could not decide what course of action was correct. He wondered how many more times Alvin would present him with such dilemmas, and smiled a little wryly at the thought. For it would make no difference either way: Alvin would do exactly as he pleased.

             As yet, not more than a dozen people outside Alvin's own family knew the truth. His parents, with whom he now had so little in common and often did not see for weeks, still seemed to think that he had merely been to some outlying part of the city. Jeserac had been the only person to react strongly: once the initial shock had worn off he had engaged in a violent quarrel with Rorden, and the two were no longer on speaking terms. Alvin, who had seen this coming for some time, could guess the details but to his disappointment neither of the protagonists would talk about the matter.