A bank of windows in the outer wall of the receiving area faced the great circle of the landing field. A six-foot partition of plastic formed the opposite wall. Set into it was an open gateway. Attendants stationed on either side of the gate watched the passengers with routine curiosity, conveying no impression of special alertness. But Hendley knew that it was not these he had to be concerned about. It was the master computer stationed by the gate, its unblinking eye waiting to record the identities of all those who passed through. The more impatient passengers were already filing through the gate. As Hendley loitered at the very end of the line, one of the attendants inspected him idly, looked away, then let his gaze wander back. Hendley began searching his uniform pockets. When he dared another glimpse, the attendant had lost interest and was no longer watching. Everything was all right. The computer might reject his identity number, but the gateway was open. It appeared that the computer did not have to control the gate to allow each passenger through. Hendley guessed that such a process caused too much congestion. When the moment came, a sudden rush would carry him through the opening. Before the guards could act, he would be merging into the stream of travelers thronging the main lobby. With luck he would escape. It was too much to hope that the computer at the city's central landing field would not possess information about the visitor whose identity disc Hendley wore. And the big man had said enough to make it clear that he was a hunted criminal. The passenger directly in front of Hendley reached the gate and flashed his identity disc. The computer emitted a low click. The passenger walked on. Hendley stepped into his place. He waved his wrist toward the computer's eye casually. He was too conditioned to computer efficiency to feel any surprise when the machine buzzed in protest. A red warning light flickered. Hendley did not wait any longer. He charged for the open gateway. A split-second later he was reeling back, his face and body bruised and battered, his brain numbed by shock. Something had risen to smash him away from the opening. Awareness seeped into his stunned mind. An invisible electronic field triggered by the computer's warning. Impregnable. The way was blocked.