She thought about that. ‘You mean I have to feed it, like a plant.’

‘There is a lot of chemical energy stored in the environment. You can tap it slowly but efficiently, like plants or bacteria, or burn it rapidly but inefficiently, like a fire. This Qax technology is smart stuff; it releases energy more swiftly than biological cells but more efficiently than a fire. In principle a nano-sown field ought to do better than a biologically planted crop . . .’

She failed to understand many of the words he was using. Though she pressed him to explain further, to help her, he was too busy.

Meanwhile Ingre, Rala’s cadre sibling, became a problem.

Despite her ideological earnestness she was weak and ineffectual, and hated the work in the fields. A drone supervisor, a collaborator, one of her own people, punished Ingre more efficiently than any Guard would have done. And when that didn’t work in motivating Ingre to work better, she cut off Ingre’s food ration.

After that Ingre just lay on her bunk. At first she complained, or railed, or cried. But she grew weaker, and lay silent. Rala tried to share her own food. But there wasn’t enough; she was going hungry herself.

Rala grew desperate. She realised that the Guards, in their brutal incompetence, were actually going to allow Ingre to die, as they had many others. She could think of only one way of getting more food.

She wasn’t sexually inexperienced; even the Qax hadn’t been able to extirpate that. Pash was easy to seduce.

The sex wasn’t unpleasant, and Pash did nothing to hurt her. The oddest thing was the spacegoer’s exoskeleton he wore, even during sex; it was a web of silvery thread that lay over his skin. But she felt no affection for him, or - she suspected - he for her. Unspoken, they both knew that it was his power over her that excited him, not her body.

Still, she waited for several nights before she asked him for the extra food she needed to keep Ingre alive.

Meanwhile, in the Conurbation, things got worse. Despite the maintenance rotas the stairwells and corridors became filthy. The air circulation broke down. The inner cells became uninhabitable, and crowding increased. Then there was the violence. Rumours spread of food thefts, even a rape. Rala learned to hide her food when she walked the darker corridors, scuttling past walls marked with bright green tetrahedral sigils, the most common graffito.

The Conurbation was dying, Rala realised with slow amazement. It was as if the sky itself was falling. People spoke even more longingly of the Qax Occupation, and the security it had brought.

One day Pash came to her, excited. ‘Listen. There’s trouble. Factional infighting among the Green Guards.’

She closed her eyes. ‘You’re leaving, aren’t you?’