After some generations of this, he pushed the conception limit up to forty-five. Then fifty.

The population in the forest dipped, but slowly started to recover. And, gradually, the lethal genes were eliminated from the gene pool.

Over time, some contact — a kind of implicit trade — opened up between the inhabitants of the lower levels and the jungle folk. But there was no incursion from below, no will to break open Deck Zero. And so, with iron determination, Uvarov enforced his huge experiment, century after century.

Arrow Maker and Spinner-of-Rope — face-painted, young-old pygmies — were the extraordinary result.

Milpitas listened, apparently bemused, as Uvarov ranted. “When I started this work the average lifespan, without AS, was about a hundred. Now we have individuals over two hundred and fifty years old…” Spittle looped across his toothless mouth. “A thousand AS years isn’t enough. Ten thousand wouldn’t suffice. I’m talking about changing the nature of the species, man…”

Milpitas laughed at him. “Was there ever a more obsessive control of any unfortunate population than that? To deny the benefits of AS to so many generations — ” The Planner shook his bare, scarred head. “To waste so much human potential, so many ‘mute, inglorious Miltons’…”

“I’m transforming the species itself,” Uvarov hissed. “And it’s working, damn you. Arrow Maker, here — ” he cast about vaguely ” — is eighty years old. Eighty. Look at him. By successively breeding out the lethal genes, I’ve — ”

“If your program was so laudable, then why did you feel it necessary to barricade yourself into the forest Deck?”

Morrow, helpless, felt as if he had wandered into an old, worn-out argument. He remembered his last interview with Milpitas, in which Milpitas had — calmly and consistently — denied the reality of the society above Deck One: a society whose independent existence had been obvious long before Arrow Maker and the others came firing darts down through the opened hatches of the Locks. And now even when confronted with Uvarov and these painted primitives — Milpitas seemed unable to break away from his own restricted world-view.

Uvarov was noisy, of alien appearance, visibly half-insane, and locked inside a partial, incomplete — yet utterly inflexible — mind-set. Milpitas, by contrast, was calm, his manner and speech ordered, controlled. And yet, Morrow reflected uneasily, Milpitas was, in his way, just as rigid in his thinking, just as willing to reject the evidence of his senses.

We’re a frozen society, Morrow thought gloomily. Intellectually dead. Maybe Uvarov is right about mind-sets. Perhaps we’re all insane, after this long flight. And yet — and yet, if Uvarov is correct about the end of the flight then perhaps we can’t afford to remain this way much longer.

With a sense of desperation, he turned to Milpitas. “You must listen to him. The situation’s changed, Planner. The ship — ”

Milpitas ignored him. He looked weary. “I’m growing bored with this. I will ask my question once more. And then you will leave. All of you.

“Uvarov, why have you come here?”

Uvarov wheeled his chair forward; Morrow heard a dull thud as the chair frame collided softly with Milpitas’ desk. “Survivalist,” he said, “the journey is over.”

Milpitas frowned. “What journey?”

“The flight of the Great Northern. Our odyssey through rime, and space, to the end of history.” His ruined face twisted. “I hate to admit it, but our factionalism serves no more purpose. Now, we have to work together — to reach the wormhole Interface, and — ”

“Why,” Milpitas asked steadily, “do you believe the journey is over?”

“Because I’ve seen the stars.”

“Impossible,” Milpitas snapped. “Your eyes are gone. You’re insane, Uvarov.”

“My people — ” Uvarov’s voice dried to a croak. Spinner-of-Rope stepped forward, took a wooden bowl of water from a rack within the body of the chair, and allowed a little of the fluid to trickle into Uvarov’s cavern of a mouth.

“My people are my eyes,” Uvarov said, gasping. “Arrow Maker climbed the tallest tree and studied the stars. I know, Milpitas. And I understand.”

Milpitas’ eyes narrowed. “You understand nothing.” He glanced, briefly and dismissively, at Arrow Maker, who returned his look with cool calculation. “I’ve no idea what this — person — saw, when he climbed his tree. But I know you’re wrong, Uvarov. We’ve nothing to discuss.”

“But the stars — don’t you see, Milpitas? There was no starbow. The relativistic phase of the flight must be over…”

Milpitas smiled thinly. “Even now, through the fog that has swamped your intellect, you’ll probably concede that one great strength of the bureaucracies you despise so much is record-keeping.

“Uvarov, we keep good records. And we know that you’re wrong. After all this time there’s some uncertainty, but we know that the thousand-year flight has at least half a century to run.”

Something stirred in Morrow’s heart at that. Somehow, he suspected, he’d never quite believed Uvarov’s pronouncement — but the authority of a Planner was something else. Just fifty years…

“You’re a damn fool,” Uvarov railed; his chair jerked back and forth, displaying his agitation.

Milpitas said coolly, “No doubt. But we’ll cope with journey’s end when it comes. Now I want you out of my office, old man. I have more than enough work to do without — ”

Morrow couldn’t help but come forward. “Planner. Is that all you have to say? The first contact between the Decks for hundreds of years — ”

“And the last, if I’ve anything to do with it.” Milpitas raised his face to Morrow; his remodelled flesh was like a sculpture, Morrow thought abstractedly, a thing of cold, hard planes and edges. “Get them out of here, Morrow. Take them back to their jungle world.”

“Was I wrong to bring them here?”

“Get them out.” Tension showed in Milpitas’ voice, and the prominence of the muscles in his neck. “Get them out.”

She wondered how she must appear to these photino creatures.

They would find it as difficult to perceive baryonic matter as she, a baryonic creature, found it to see them. Perhaps the birds saw a pale tetrahedron, the faint dark-matter shadow of the exotic matter Interface framework which formed the basis of her being. Perhaps they caught some dim sense of the wormhole itself, the throat of space and time through which she pumped away the heat which would otherwise destroy her.

The old theories had predicted dark-matter particles colliding with the swarming protons of the Solar core, absorbing a little of their energy and so transporting heat out from the fusing heart. This was how, it was thought, dark matter cooled the Sun.

She saw now that these notions had been right in essence, but too crude. The birds absorbed Solar heat energy. They fed on interactions with protons in the plasma. Incorporating energy from photino-proton interactions within their structures, the birds grew, and spiraled out from the hotter, denser heart of the Sun, taking the heat energy with them.

The ancient theorists had envisaged a particle-based physical process to extract core heat, and so suppress the fusion processes there. The truth was, the birds fed on the Sun’s heat.

And, by feeding — like unwise parasites — they would eventually kill their host.

Unwise — unless, of course, that had been the intention all along.

Lieserl had learned about the Qax.

The Qax had originated as clusters of turbulent cells in the seas of a young planet. Because there were so few of them the Qax weren’t naturally warlike — individual life was far too precious to them. They were natural traders; the Qax worked with each other like independent corporations, in perfect competition.