Someday the Qax would be gone, Parz knew. Maybe it would be humanity that would do the overthrowing; maybe not. In any event there would be trade under the governance of a new race, new messages and matériel to carry between the stars. New wars to fight. And there would be the Spline, the greatest ships available — with the probable exception, Parz conceded to himself, of the unimaginable navies of the Xeelee themselves — still plying between the stars, unnoticed and immortal.

The small viewport glowed briefly crimson, its flawed plastic sparkling with laser speckle. Then a translator box built somewhere into the fabric of the flitter hissed into life, and Parz knew that the Spline had established a tight laser link. Something inside him quailed further now that the climax of his journey approached; and when the Qax Governor of Earth finally spoke to him in its flat, disturbingly feminine voice, he flinched.

"Ambassador Parz. Your torso is arranged at an awkward angle in your chair. Are you ill?"

Parz grimaced. This was the nearest, he knew, that a Qax would ever come to a social nicety; it was a rare enough honor, accorded him by his long relationship with the Governor. "My back is hurting me, Governor," he said. "I apologize. I won’t let it distract my attention from our business."

"I trust not. Why don’t you have it repaired?"

Parz tried to compose a civil answer, but the forefront of his consciousness was filled once more with a distracting awareness of his own aging. Parz was seventy years old. If he had lived in the years before the coming of the Qax, he would now be entering the first flush of his maturity, he supposed, his body cleansed and renewed, his mind refreshed, reorganized, rationalized, his reactions rendered as fresh as a child’s. But AntiSenescence technology was no longer available; evidently it suited the Qax to have humanity endlessly culled by time. Once, Parz recalled, he had silently raged at the Qax for this imposition above all: for the arbitrary curtailment of billions of immortal human lives, for the destruction of all that potential. Well, he didn’t seem to feel anger at anything much anymore…

But, he thought bitterly, of all the plagues that the Qax had restored to mankind, he would never forgive them his aching back.

"Thank you for your kindness, Governor," he snapped. "My back is not something that can be fixed. It is a parameter within which I must work, for the rest of my life."

The Qax considered that, briefly; then it said, "I am concerned that your functionality is impaired."

"Humans no longer live forever, Governor," Parz whispered. And he dared to add: "Thank God." This was the only consolation of age, he reflected tiredly, wriggling in the chair to encourage it to probe harder at his sore points — that meetings like these must, surely soon, come to an end for him.

"Well," said the Qax, with a delicate touch of irony about its sophisticated artificial voice, "let us proceed before your bodily components fail altogether. The wormhole. The object is now within the cometary halo of this System."

"The Oort Cloud, yes. Barely a third of a light-year from the Sun." Parz waited a few seconds for the Qax to indicate specifically why he’d been brought here. When the Qax said nothing he drew data slates from his briefcase and scrolled down lists of facts, diagrams, running over the general briefing he had prepared earlier.

"It is an ancient human artifact," the Qax said.

"Yes." Parz retrieved an image on his slate — glowing frameworks against a salmon-pink backgrounds — and pressed keys to dump it through the tabletop and down the link to the Governor. "This is a video image of the launch of the artifact from the orbit of Jupiter, some fifteen hundred years ago. It was known as the Interface project." He touched a fingernail to the slate to indicate the details. "In essence, two tetrahedral frameworks were constructed. Each framework was about three miles wide. The frameworks threaded the termini of a spacetime wormhole." He looked up, vaguely, in the direction of the ceiling. Not for the first time he wished he had some image of the Governor on which to fix his attention, just a little something to reduce the disorienting nature of these meetings; otherwise he felt surrounded by the awareness of the Governor, as if it were some huge god. "Governor, do you want details? A wormhole permits instantaneous travel between two spacetime points by—"

"Continue."

Parz nodded. "One tetrahedral framework was left in orbit around Jupiter, while the other was transported at sublight speeds away from the Earth, in the direction of the center of the Galaxy."

"Why that direction?"

Parz shrugged. "The direction was unimportant. The objective was merely to take one end of the wormhole many light-years away from the Earth, and later to return it."

Parz’s table chimed softly. Images, now accessed directly by the Qax, scrolled across his slate: engineering drawings of the tetrahedra from all angles, pages of relativistic equations… The portal frameworks themselves looked like pieces of fine art, he thought, or, perhaps, jewelry resting against the mottled cheek of Jupiter.

"How were the tetrahedra constructed?" the Qax asked.

"From exotic matter."

"From what?"

"It’s a human term," Parz snapped. "Look it up. A variant of matter with peculiar properties that enable it to hold open the termination of a wormhole. The technology was developed by a human called Michael Poole."

"You know that when humankind was brought into its present close economic relationship with the Qax, the second terminal of this wormhole — the stationary one, still orbiting Jupiter — was destroyed," the Governor said.

"Yes. You do tend to destroy anything you do not understand," Parz said dryly.

The Qax paused. Then it said, "If the malfunctioning of your body is impairing you, we may continue later."

"Let’s get it over." Parz went on, "After fifteen centuries, the other end of the wormhole is returning to the Solar System. It is being towed by the Cauchy, a freighter of ancient human design; we speculate that relativistic effects have preserved living humans aboard the freighter, from the era of its launch."

"Why is it returning?"

"Because that was the mission profile. Look." Parz downloaded more data into the table. "They were due to return about now, and so they have."

The Qax said, "Perhaps, since the destruction of the second, stationary tetrahedron, the wormhole device will not function. We should therefore regard this — visit from the stars — as no threat. What is your assessment?"

"Maybe you’re right."

"How could we be wrong?"

"Because the original purpose of the Interface project was not to provide a means of traveling through space… but through time. I am not a physicist, but I doubt that your destruction of the second terminus will have destroyed its functionality."

Parz’s slate now filled with a simple image of a tetrahedral framework; the image had been enhanced to the limit of the telescopic data and the picture was sharp but bleached of detail.

The Governor said, "You are implying that we may be witnessing here a functioning time machine? A passage, a tunnel through time that connects us to the humanity of fifteen centuries ago?"

"Yes. Perhaps we are." Parz stared at the image, trying to make out details in the faces of the tetrahedron. Was it possible that just beyond those sheets of flawed space was a Solar System free of the domination of the Qax — a system peopled by free, bold, immortal humans, brave enough to conceive such an audacious project as the Interface? He willed himself to see through these grainy pixels into a better past. But there was insufficient data in this long-range image, and soon his old eyes felt rheumy and sore, despite their enhancements.