He gave all of his attention to his plays. Shortly after he returned to this grim concentration, the tide of the duel changed. Hendley thought he detected a fixed sequence in the robot's guesses. Betting experimentally, he won. Again. Another win. With increasing sureness he raised his bets boldly. In half a dozen plays he recouped all of his losses and more. The run continued. He couldn't lose. Then, abruptly, the pattern of the robot's moves disappeared. Hendley grinned. He had three-fourths of the chips on the table now--he had the advantage. More important, he had proved to himself that the robot was vulnerable. A machine didn't adjust as quickly as a human being, perhaps because it felt no fear. Hearing a muttering in the crowd, Hendley stared at the ring of faces. He was surprised to see a number of the Freemen smiling at him encouragingly. So they were not all waiting for him to lose! Some of them appeared disappointed, but almost as many were pulling for him. The knowledge buoyed him tremendously. The game dragged on. Hendley kept searching for another weakness in the robot's play, but without success. The stacks of chips became even again. Hendley kept varying his guesses, changing his bets at random from high to low number combinations, but slowly the robot drew ahead again. At last Hendley admitted to himself that, if the game went on long enough, the robot would inevitably win. But the game ended at dawn. If Hendley held out until then he could cash in his chips. He wondered how long he had been playing. Hours, it seemed. His body ached, and the continuous tension had begun to affect his nerves. That was part of the robot's strength, he thought. It was tireless. Moreover, it did not make the small errors Hendley occasionally made from carelessness or lack of concentration. With the rest of the play relatively even, these infrequent slips alone could account for the robot's superiority. It seemed clear that the robot had made corrections to prevent the one serious blunder of consistency it had made. That had been Hendley's only chance to win. Now all he could hope to do was stave off defeat until the first light of day.