Nobody on the Grand Unified knows what their ship is even called, or that it's a ship, or what the words "generation ship" mean. All they know is that they live in a fixed, closed, finite space, very approximately cylindrical, lit by a blindingly bright thread down the main axis, with parkland, residential areas, business, industrial areas...

Wealthy areas... less wealthy areas... slums.

All they know is that these scant few dozen square kilometres of concave land are the length and breadth of their universe. There's nothing outside of it, there's nowhere else to go. Pressure has been rising for a generation and a half. Dissatisfaction has been spiralling and the lower echelons of the bottled society are beginning to push back.

The oxygen system needs maintenance. The forests need tending. The wheat needs planting and the nitrogen processors need refitting. It's a completely closed system — almost every grain of matter on the whole ship is accounted for. There is a limitless source of energy at one cap of the habitat, such a preposterous quantity of energy that it can be adapted trivially to handle even the most wasteful and inefficient recycling processes. All that matters is the cycle. Nothing leaves. The hull is impervious from the inside and the outside and there isn't a single window. The ship vents heat, horrible amounts of it, but not a single particle of actual matter. That's the rule. A rule elevated to the level of a religion. Everything is important. Everything is critical. Everything comes back.

And despite all of that, still, power imbalance.

That's the part that gnaws away. That's the part which hacks away at young Jack's soul. She knows the stories, how close previous generations of their little society came to catastrophic failure, how slow the rebuild was. Like anybody in her cohort, like all her friends, like her late mentor Oth and her best friend Syril and her close-ally-and-maybe-hopefully-someday-something-more Mnolam and like... her tragically departed father and mother... she comprehends, at a near-spiritual level, the importance of the cycle. Nobody in the meeting, nobody who's part of the uprising doesn't understand the cycle.

But does there have to be the imbalance? Do there have to be the superior and the downtrodden? Does it have to hurt so much, every day? Do they always have to be so tired, and overheated, and hungry?

Jack has been part of this uprising for three years. She thinks. The adults in charge have known she'd be part of it for longer than that. When she joined, as she inevitably had to, they knew she had the combination of qualities they were looking for, not in a leader, as such, but in a figurehead: verve, wits, a bold spirit, and, let's be honest, extreme conventional attractiveness. But she's turned out to be the leader, too. She's learned to fight.

Now she's one of a thousand people charging up the grand staircase towards the north cap of the habitat, ascending towards the mansions and offices and seat of power of the nervous and panicky Executive class. There are no firearms in the habitat, but there are edge weapons and bows, and although the intermediate layer — the thick, grimy wall which, in every iteration of this scenario, in every society, separates the Executive from the Consequences — fights back hard, they quickly lose out.

At the top of the staircase, in the place where the habitat spins faster than everywhere else, but where there's still relatively little gravity, and the people are lankly and graceful and willowy and fragile, the atmosphere is one of unprecedented dread.

Almost unprecedented. Unprecedented as far as any of them know first-hand, or from stories.

"And yet," Vessn says, "there is provision for this."

"This could be the end," Cerist says. His face is pulled into an uncharacteristic rictus of tension. Wow, that's a bad sentence. "I say, Prime Executive, this really could be it. The end of the ship. The end of human existence inside the Grand Unified."

"The ship is sound," Vessn says. "This much is fully provided for, as you well know. There is nothing, nothing, which human society inside this capsule can do to break the capsule itself. Grand Unified will reach Earth intact... three and a half thousand years from now, of course."

"It'll be a ghost ship," Cerist wails. "A dark hollow full of the dead! And never another human, never in all history. The death of a self-aware universe. What... I suddenly realise I don't know what happens to... ah, to a body which is not fully recycled?"

"It decays," Vessn says. "It shrivels up until all that is left is a thin layer of grey skin, hollow eye sockets and a skeleton. In the existence of Grand Unified, it has happened a handful of times. There are old records. Disturbing."

"And that's it? Not just for us. For everybody in this world." Cerist floats over to the grand window and watches the mayhem outside. It's getting closer. He spots a particularly violent encounter, one speck eviscerating another on a high wall, far down the staircase curve, and flinches. There is nowhere to retreat to from here. "The Grand Unified needs us. The Builders provided for an Executive, and... everybody else. Without all the training, education, the physics and chemistry and sociology it takes to maintain a capsule society, how will they manage? This deviates from the Plan."

"The Plan?" Vessn asks, rhetorically. He snorts. He pulls himself, hand over hand, into an upper corner of the office, and pulls a secret book out of the trio of bookshelves in that corner, and in doing so causes a panel in what is, from Cerist's perspective at least, currently the ceiling, to unlatch. "The Plan? Singular?"

"Prime Executive?"

The secret panel unfolds, revealing a passage. Vessn pulls himself up and through it, and along a corridor towards a dark hidden vault. At that moment, rebels are beginning to storm the residence, and Cerist hurries after his superior.

"Prime Executive?"

"Join me," Vessn says. "Be seated and wait. Partake of this." He lightly tosses a little ceramic dish at Cerist, which is filled with a black and green clay-like substance. Cerist catches it, takes the suggested seat, and nervously rubs a fingertip in the clay, then against his gum.

"Is there a plan for this?" Cerist asks, trying to resist the urge to lick the clay off again.

"There is. Ah! The fêted Jack of the Silver. For a third time we meet, and as ever you have a knife in your hand. I think the steak knife suited you better. Combined with the stolen cleaner's uniform? I liked the improvised look. This..." He gestures at her look, her stance, her fierce visage, her armour. Her bloodied combat knife. "Too much. Too calculated."

Cerist begins to fade out.

"You die today, Vessn," Jack says.

"I don't doubt it. You won, Jack," Vessn says. "There are a hundred Plans. Navigating them requires some deftness, a great deal of improvisation. A Plan runs for as long as it can and then a rebel like Jack here storms the palace of the Executive... and the Plan folds itself up for another day, and a different Plan begins. Jack, the world is yours." He holds out a document.

"What is this?"

"Instructions," Vessn says. "Your ideals will hold out for... a few years. More if you focus hard. The Plans will help you along for as long as you can. But 'as long as you can' won't be forever. You'll compromise, and then you'll have to think of something else, and then... a different Plan. And then another one again, and then maybe fifty years from now you'll wake up and what do you know, you'll be heading an Executive, and a youngster with an edged weapon will be coming down the corridor after you, too."

"Take him," Jack orders, and they bind Vessn's wrists and escort him away.

"Human civilisation is not a steady state," Vessn says, over his shoulder, to Jack, as she follows him. "Human civilisation cannot survive in an enclosed space without changing. It doesn't matter where it starts. The Grand Unified could never have been built that way. There was no way that a living human would make it to Earth that way. Jack, this is chaos! In the mathematical sense! A society ricocheting through a many-dimensional phase space, with no fixed point. This is a dynamic society. It's built that way.

"Periodic revolution. It's built into the system. It's the only way we can go on. It's a cycle, Silver."

They throw him down the long axis. He drifts almost parallel with the light tube for almost a kilometre, shrinking, tumbling end-over-end in what is almost freefall, past the great staircase, until he drifts over the city at its base, and then the plains. But then, inexorably, the movement of air starts to tug at him. And he is dragged away from the axis, slowly, and then faster, and he falls.

And back in his office, Jack sits down in the negligible gravity, and begins reading.

Next: CryptoMatter