found their surroundings completely familiar, yet to Alvin and Khedron this was a glimpse of another world. The purpose of the long, streamlined machine that lay aimed like a projectile at the far tunnel was obvious, but that made it none the less novel. Its upper portion was transparent, and looking through the walls Alvin could see rows of luxuriously appointed seats. There was no sign of any entrance, and the entire machine was floating about a foot above a single metal rod that stretched away into the distance, disappearing in one of the tunnels. A few yards away another rod led to the second tunnel, but no machine floated above it. Alvin knew, as surely as if he had been told, that somewhere beneath unknown, far-off Lys, that second machine was waiting in another such chamber as this.
Khedron began to talk, a little too swiftly.
"What a peculiar transport system! It could only handle a hundred people at a time, so they could not have expected much traffic. And why did they go to all this trouble to bury themselves in the Earth if the skies were still open? Perhaps the Invaders would not even permit them to fly, though I find that hard to believe. Or was this built during the transition period, while men still traveled but did not wish to be reminded of space? They could go from city to city, and never see the sky and the stars." He gave a nervous laugh. "I feel sure of one thing, Alvin. When Lys existed, it was much like Diaspar. All cities must be essentially the same. No wonder that they were all abandoned in the end, and merged into Diaspar. What was the point of having more than one?"
Alvin scarcely heard him. He was busy examining the long projectile trying to find the entrance. If the machine was controlled by some cental or verbal code order, he might never be able to make it obey him, and it would remain a maddening enigma for the rest of his life.
The silently opening door took him completely unawares. There was no sound, no warning when a section of the wall simply faded from sight and the beautifully designed interior lay open before his eyes.
This was the moment of choice. Until this instant, he had always been able to turn back if he wished. But if he stepped inside that welcoming door, he knew what would happen, though not where it would lead. He would no longer be in control of his own destiny, but would have placed himself in the keeping of unknown forces.
He scarcely hesitated. He was afraid to hold back, being fearful that if he waited too long this moment might never come again-or that if it did, his courage might not match his desire for knowledge. Khedron opened his mouth in anxious protest, but before he could speak, Alvin had stepped through the entrance. He turned to face Khedron, who was standing framed in the barely visible rectangle of the doorway, and for a moment there was a strained silence while each waited for the other to speak.
The decision was made for them. There was a faint flicker of translucence, and the wall of the machine had closed again. Even as Alvin raised his hand in farewell, the long cylinder started to ease itself forward. Before it had entered the tunnel, it was already moving faster than a man could run.
There had been a time when, every day, millions of men made such journeys, in machines basically the same as this, as they shuttled between their homes and their humdrum jobs. Since that far-off day, Man had explored the Universe and returned again to Earth-had won an empire, and had it wrestled from his grasp. Now such a journey was being made again, in a machine wherein legions of forgotten and unadventurous men would have felt completely at home.
And it was to be the most momentous journey any human being had undertaken for a billion years.
Alystra had searched the Tomb a dozen times, though once was quite sufficient, for there was nowhere anyone could hide. After the first shock of surprise, she had wondered if what she had followed across the park had not been Alvin and Khedron at all, but only their projections. But that made no sense; projections were materialized at any spot one wished to visit, without the trouble of going there in person. No sane person would "walk" his projected image a