The slightly springy material of the sidewalk gave just a trifle with each step, so that he felt an added sense of acceleration, as if he was running so quickly that he could just take off above the treetops. His feet were strangely cold, although the air was maintained at a constant 73.2, and his heart was pounding when he finally came out onto the five-acre area of artificial trees and fields that surrounded the city complex.

Benches were neatly placed around the landscape, each with one bush beside it and a potful of simulated flowers. Now at suppertime the area was vacant. Some of the flowers were growing brittle. Scientists were working on a new material that might actually reproduce itself, or at least repair itself, maintaining a more natural look. Proteus wondered if he’d ever come back, and if he did, whether or not the new plastic “life” would replace the old.

A week ago he’d carefully cut out a whole chunk of “grass” and placed his survival kit and supplies beneath. Now he retrieved them hurriedly. It would be dark at seven, when the day lights automatically lowered to minimum illumination. A panicky feeling flickered behind his forehead. Ignoring it, he inflated his aero-skis, put his survival kit over his back, and glided through the quiet air. The skis worked by reacting against the air beneath them. His were a boy’s set, allowing only an elevation of six feet; but they could go fast enough.

He was too much in a rush now to enjoy sky-skiing as he usually did, but his love of the sport paid off. He was an expert at riding the soft eddies of regulated air that rose and fell. And the skis could go almost thirty miles an hour. The light began to dim to early twilight. It would last for forty-five minutes. He wasn’t nearly as obvious as he would have been in maximum daylight, and if anyone saw him he’d just look like any boy, sky-skiing—if you didn’t happen to notice his direction. Because now he was heading away from the complex.

In another half-hour he was at his destination. He floated down, deflated the skis, and tied them around his waist just as the inner sky turned to night light. The ramp entrance had taken him months to discover. Now it was only ten minutes away. No one came to this area except maintenance crews. Here, no effort had been made to decorate; a series of gray sprawling plastoid buildings stood silently. He reached the ramp entrance. None of them were guarded; no one but the women crews used them to begin with.