Ship Three was directly ahead of him. It was a drum, a squat cylinder about a kilometre across and half as tall. It sat at the bottom of its own crater, for Port Sol ice had been gouged out and plastered roughly over the surface of its hull. It looked less like a ship than a building, he thought, a building coated by thick ice, as if long abandoned. But it was indeed a starship, a ship designed for a journey of not less than centuries, and fountains of crystals already sparkled around its base in neat parabolic arcs: steam from the Ship’s rockets, freezing immediately to ice. People milled at its base, running clumsily in the low gravity, and scurried up ramps that tongued down from its hull to the ground.

Rusel abandoned the car, tumbled out onto the ice and ran towards the nearest ramp. There was another stomach-churning wait as an Enforcer in glowing yellow checked each identity. At last, after another dazzling flash of laser light in his eyes, he was through.

He hurried into an airlock. As it cycled it struck him that as he boarded this Ship, he was never going to leave it again: whatever became of him, this Ship was his whole world, for the rest of his life.

The lock opened. He ripped off his helmet. The light was emergency red, and klaxons sounded throughout the ship; the air was cold, and smelled of fear. Lethe, he was aboard! But there could only be a minute left.

He ran along a cold, ice-lined corridor towards a brighter interior.

He reached an amphitheatre, roughly circular, carpeted by acceleration couches. Andres’s voice boomed from the air: ‘Get into a couch. Any couch. It doesn’t matter. Forty seconds. Strap yourself in. Nobody is going to do it for you. Your safety is your own responsibility. Twenty-five seconds.’ People swarmed, looking for spare couches. The scene seemed absurd to Rusel, like a children’s game.

‘Rus! Rusel!’ Through the throng, Rusel made out a waving hand. It was Diluc, his brother, wearing his characteristic orange skinsuit. ‘Lethe, I’m glad to see you. I kept you a couch. Come on!’

Rusel pushed that way. Ten seconds. He threw himself down on the couch. The straps were awkward to pull around the bulk of his suit.