They were standing in a doorway out of the stream of pedestrians. Suddenly Vickers' mouth fell open. He stared at the man in startled disbelief. It was himself! The resemblance was too perfect. The same close-cropped black hair and Jupiter-enlarged muscles. The same short, straight nose, wide, thin-lipped mouth, square jaw. Even the same transparent inner lids lowered over pale gray eyes. It was like looking into a mirror. Vickers felt his mouth go dry. "Who are you?" he demanded harshly. "You recognize me? Good." The man grinned, began to edge away. Vickers lunged for him. But the fellow eluded his grasp, slipped into the stream of traffic like an eel. He was rapidly being swallowed up by the crowd. Vickers ploughed after him. There was something afoot--something dangerous to himself, he felt. He was determined not to lose sight of his double and opened his nictitating lids.... Instantly, the scene about the busy spaceport changed. It took on a vaporous unreality like an x-ray photograph. The people, the buildings, even the pavement underfoot became tenuous as smoke. He could see right through them. It always frightened Vickers a little to use his full vision, taking him a second to adjust. Then he located his double about ten steps ahead. He could make out the misty outlines of elevators in the man's flashing heels. So that was how he'd given himself the necessary height. Pads filled out his frame reproducing Vickers' Jupiter-trained muscles. The nictitating lids had been cleverly simulated by contact lenses. But why? Why should anyone go to all that trouble to disguise himself exactly like Vickers--even to the ill-fitting gray suit? There was something sinister about the whole affair. Just then Vickers tripped, lost his precarious balance and fell sprawling. He scrambled to his feet in time to see the stranger leap into an air taxi. "Look at his eyes!" a woman cried out at his elbow. "Look at his eyes!" * * * * * Vickers hastily lowered his inner lids, cursing under his breath. There wasn't another cab in sight. He'd better clear out before he was the focal point of a riot. Normal humans weren't fond of mutants. Already a crowd was collecting. Vickers heard angry mutterings. He forced his way through the press bull-like. Suddenly he found his path blocked by two determined-looking men. "Hold on," said the man on the outside and put his hand on Vickers' chest. He was blond with cold, pale blue eyes. "What's your hurry?" Vickers started to thrust them aside when he felt the second man jam a gun into his ribs. "Vickers, aren't you?" asked the blond man. "What of it?" "Come along." He jerked his chin toward an air taxi. "Don't make a fuss." "Where?" "Headquarters." The man produced an ISP card. "We tried to catch you at the ship, but you'd left."