Ryd watched in painful suspense. There was no sound in his ears save for the hard, dry shrilling of the ray as it bit into the steel. It seemed to be crying: _run, run_--but he remembered the power that knew how to punish better than the law, and stood still, shivering. The lock gave way and the door slipped aside. A light went on inside, and Ryd's heart stopped, backfired, and started again, raggedly. The same automatic mechanism that had turned the lights on had started the air-fresher, which picked up speed with a soft whine, sweeping out the long-stale atmosphere. Mury motioned to Ryd to follow him in. * * * * * It was still musty in the narrow passage, between the closely-pressing walls, beneath the great tubes and cable sheathings that fluted the ceiling overhead. A stairway spiraled up on the right to the control cupola somewhere overhead; even in the airtight gallery a thin film of dust lay on every step. Up there were the meters and switches of the disused terminal facilities of the spaceport; beyond the metal door marked CAUTION, just beyond the stairwell, lay the long runway down which the ships of space had glided to be serviced, refueled, and launched into the sky once more by now dormant machines. "Wait," said Mury succinctly; he vanished up the spiral stair, his long legs taking two steps at a time. After an aching minute's silence, he was back. All was clear as seen from the turret-windows overhead. They emerged in shadow, hugging the wall. Almost a quarter of a mile to the right the megalith of the Communications Tower, crowned with many lights where the signal-men sat godlike in its summit. Its floodlights shed a vast oval of light out over the mesa, where the mile-long runways--no longer polished mirror-like as in the days of Dynamopolis' glory--stretched away into the darkness of the table land. A handful of odd ships--mere remnant of the hundreds that Pi Mesa port had berthed--huddled under the solenoid wickets, as if driven together by the chill of the thin, knife-like wind that blew across the mesa. As the two paced slowly across the runways, Ryd had a sense of protective isolation in the vast impersonality of the spaceport. Surely, in this Titanic desolation of metal slabs and flat-roofed buildings, dominated by the one great tower, total insignificance must mean safety for them. And indeed no guard challenged them. There were armed men watching for all intruders out on the desert beyond the runways, but once inside, Ryd's borrowed blue seemed to serve as passport enough. Nonetheless, the passport's knees were shaking when they stood at last, inconspicuous still, at the shadowed base of the Communications Tower.