The portal grew steadily in Parz’s view. The Spline must already be inside the squeezed-vacuum exoticity zone that surrounded the mouth of the wormhole itself, and soon the portal was so close that Jasoft had to press his faceplate against the warm Spline lens to make out its vertices.

"It’s almost time," he whispered.

"Yes, Ambassador," the Qax growled. "Almost time."

The words that sounded in his headpiece were — as ever — a bland, synthesized human voice, the product of a translator box somewhere in the Spline. "Qax, I wish I knew what you were feeling."

The Qax paused for some seconds. Then, "Anticipation. Anticipation of satisfaction. My goal is close. Why do you ask this?"

Jasoft shrugged. "Why not? I’m interested in your reactions. Just as you must be interested in mine. Otherwise, why would you have brought me here?"

"I’ve explained that. I need a way into human perceptions."

"Rubbish," Parz said without anger. "Why do you bother to justify yourself in that way? Qax, you’re traveling back in time to destroy humanity — to eradicate forever the unlimited potential of a species. What do you care about human perception?"

"Jasoft Parz," the Qax said, its voice almost silky now, the relish audible, "you are the only human to return through time with this Qax expedition. Fifteen centuries ago humans were still largely cooped up in the dull star system of their birth. When we have destroyed the home planet — and scoured the neighboring worlds and spaces — you will be the only human left alive. And with the termination of your species’s world line, you will also be the last human. How will that feel?"

Parz felt his lifetime of compromise — of diplomacy — weigh down on him, a freight of age still heavy despite his AS rejuvenation. He tried, as he’d tried before, to comprehend the significance of the Qax’s monstrous act. Surely it was his duty, as the last human, to feel the pain of this crime, to suffer on behalf of his race.

But he couldn’t. It was beyond him. And, he thought, he had moved beyond hope.

He wondered how he’d feel, though, if he had children of his own.

He nodded, infinitely tired. "So. You’ve brought me here so you can watch me, as I watch my race die. I’ve not understood before; I guess I was hoping for — what? nobility? — from the murderer of my species. But it really is as petty as that. My reaction, the grief of one man, will dramatize for you the emotional significance of the event. It will heighten your pleasure. Won’t it?"

"Pleasure? I am not psychopathic, Jasoft Parz," the Qax said. "But the sweetness of my revenge will be great."

"Revenge for what?"

"For the destruction of my own world, of the home of the Qax, by the actions of a single human."

Parz had been told something of the story.

A few centuries after Parz’s era, there would be a human: Jim Bolder, an unremarkable man.

The Qax would try to employ Bolder, to exploit him for gain. But Bolder would deceive them — somehow trick them into turning starbreakers on their own sun.

The new Governor came from a future in which the comparatively lenient Occupation of Earth had led, inexorably, to the destruction of the Qax home world, to a diaspora in which dozens of the fragile Qax had perished. In this timeline the Qax were marginalized; humans, freed of the Occupation, grew far stronger.

The Qax wanted to change all that.

Ironically, Parz had come to understand, the rebellion of the Friends of Wigner had nothing to do with the ultimate collapse of the Occupation, in this timeline. Whatever the rebels’ scheme was it was seen as irrelevant by the Qax — in fact, the sequence of time bridges initiated by the rebellion was actually an opportunity for the Qax to move back into time, far beyond Bolder, and to rectify their earlier leniency.

Parz, baffled and disturbed by the philosophy of it all, wondered if a multiplicity of variant worlds would be initiated by this series of trips into the past, of closed timelike curves. The original variant, the prime timeline, saw no impact on events from either the rebels’ activities or the Qax’s actions; the timeline would unfold with relentless logic to the Qax diaspora. The Qax, now, hoped to return through time to crush humanity before such events had a chance to occur; this second variant would see no diaspora and the emergence — presumably — of the Qax as the dominant species in the absence of mankind. The rebels, with their unknown project, must hope to initiate a third variant in which the Occupation would be crushed before the time of Jim Bolder — of whom, of course, the rebels could have no knowledge; to them the Occupation must have looked immense and eternal.

But even that wasn’t the end of it, Parz realized; for presumably the actions of the various groups of time travelers would interact to set off a fourth, fifth, or sixth variant…

But most human philosophers seemed to agree, now, that only one of these variants could be considered "real"; only one could be collapsed into actuality by the observation of conscious minds.

Parz pressed his face against the warm lens material; it yielded like thin rubber. The electric blue struts of the Interface portal had almost embraced the Spline now; the nearest face, which already blocked out the stars, the moons of Jupiter, was dark and empty, its blackness relieved only by a hint of autumn gold. Parz twisted his head about. He caught a glimpse of the second Spline he’d seen earlier; it hovered above and behind the Qax’s ship, following it toward the portal. "Some armada," he said. "Two ships?"

"Two are all that is required. The humans of fifteen centuries ago will have no means of defense against the weaponry of the Spline craft. The second craft will destroy the vessel of these rebels from your present — these Friends of Wigner — while my ship will besiege Earth."

Parz felt his throat tighten. "How?"

"Starbreaker beams."

Parz closed his eyes.

"Maybe your revenge won’t be so sweet," he said at random. "What about causality? Maybe I’ll pop out of existence as soon as my ancestors are destroyed. Maybe you will too. Have you thought about that? And then the destruction of your world by this human hero will never have happened… and you’ll have no reason, or means, to travel through time to assault the Earth." But then, he thought further, if the Qax did not travel back through time, surely humanity would survive to destroy the Qax world after all… "We’ll be caught in a causality loop, won’t we?"

"Jasoft Parz, causality does not operate in such a simplistic fashion. In such a circumstance the different outcomes may all exist simultaneously, like the probabilities expressed by a quantum function. But only one of those possibilities will be collapsed to actuality—"

"Are you sure?" Parz said grimly. "You’re talking about destroying a race… about altering history on a cosmic scale, Qax."

"Yes, we are sure. My intention is to close off all probabilities, all variants of reality in which humanity can survive. After the reduction of your system, you will be the only human left alive."

"And you and I will disappear into nonexistence," Parz said grimly.

"No," the Qax said. "But the timeline from which we emerged will no longer exist, as a potentiality. We will be stranded, out of time. But my job will be done."

Yes, Parz thought, what it’s saying is possible. The Qax was plotting not just the destruction of humankind but the destruction of all variant realities in which humanity might have survived. It was more than genocide, he saw; it was a murder of reality.

The Qax’s calculation somehow penetrated Parz’s dulled heart more deeply than anything else. How could a sentient being discuss such gruesome events — the destruction of species, of worlds, of timelines — in the language of cold logic, of science?