If he could maneuver his way into the shadow; if the robot followed him there…

The coolness might calm those disordered positronic paths. It might become tamer, more reasonable, and Lucky might be spared the necessity of its destruction. Lucky dodged again, and again the robot rushed past, its metal legs kicking up spurts of black grit that settled back to Mercury promptly and cleanly since there was no atmosphere to keep it in suspension. It was an eerie chase, the tread of man and robot hushed and silent in the vacuum.

Lucky's confidence grew somewhat. The robot's movements had grown jerkier. Its control of the gears and relays that manipulated its limbs was imperfect and growing more so.

Yet the robot was making an obvious attempt to head him off from the shadow. It was definitely and beyond any doubt trying to kill him.

And still Lucky could not bring himself to use the blaster.

He stopped short. The robot stopped too. They were face to face, five feet apart, standing on the black patch of iron sulfide. The blackness seemed to make the heat all the greater and Lucky felt a gathering faintness. The robot stood grimly between Lucky and the shade.

Lucky said, "Out of my way." Talking was difficult.

The robot said, "I have been told to prevent any interference with the orders given me. You have been interfering."

Lucky no longer had a choice. He had miscalculated. It had never occurred to him to doubt the validity of the Three Laws under all circumstances. The truth had come to him too late, and his miscalculation had brought him to this: the danger of his own life and the necessity of destroying a robot.

He raised his blaster sadly.

And almost at once he realized that he had made a second miscalculation. He had waited too long, and the accumulation of heat and weariness had made his body as imperfect a machine as was the robot's. His arm lifted sluggishly, and the robot seemed to be twice life-sized to his own reeling mind and sight.

The robot was a blur of motion, and this time Lucky's tired body could not be driven into quick enough movement. The blaster was struck from Lucky's hand and went flying. Lucky's arm was clamped tight in the grip of one metal hand, and Ms waist was embraced by a metal arm.

Under the best of circumstances, Lucky could not have withstood the steel muscles of the mechanical man. No human being could have. Now he felt all capacity for resistance vanish. He felt only the heat.

The robot tightened its grip, bending Lucky backward as though he were a rag doll. Lucky thought dizzily of the structural weakness of the inso-suit. An ordinary space-suit might have protected him even against a robot's strength. An inso-suit could not. Any moment, a section of it might buckle and give.

Lucky's free arm flailed helplessly, his fingers dragging into the black grit below.

One thought flicked through his mind. Desperately he tried to drive his muscles into one last attempt to fend off what seemed inevitable death at the hands of a mad robot.