It happens twice a day (whatever a day is). Everything happens twice a day; he is allowed to sleep twice a day, he is fed twice a day, he can relieve himself twice a day.
And, twice a day, he creates food for his people.
He sits on the edge of his bed and looks up at the thing on the wall. He cannot know what it says because he cannot read ... or can no longer read. But it changes at regular intervals and he knows it somehow marks the way time moves on, passes by. Though all time is the same to him now.
The grey walls are empty apart from the device. The floor is empty apart from his bed, his chair and his table. And then there is the barrier. It rises nearly to his waist and prevents him from climbing into the place where the water is. But he can see through it.
He hates the water because he knows the water is why he is how he is. Here, on the lower levels of the city, rivers or ponds or streams are miles and miles above him. And all filled with poison. Yet there is water here.
He sits at his solitary table and stirs the brownish paste with his spoon, knowing it must be full of chemicals, drugs to make him compliant and to maintain his genetic 'gift'. But what choice does he have? He needs sustenance. One man's poisson is another man's poison, he thinks and giggles to himself for a moment. He doesn't like the sound, finding it strange and painful, and stops suddenly. He wonders where the curious phrase came from.
Once he had refused to eat. For three days he had pushed away the plate of vaguely flavoured savoury mush they provided him with. Then they took him and did something to him. He can't remember what; he struggles to remember anything at all now.
He was foolish to defy them, they told him. He does remember them saying that. After all, what were the desires of one man against the crushing needs of billions of hungry mouths?
He still has memories, but they are all mis-shapen and he fears they may only be dreams. Yes, he's sure he has memories - some sort of memories, at least - of a childhood spent in the filth-strewn streets on the surface; dodging among the mountains of detritus between home and school, face masked against the stench. But that was a million years ago, or more.
There had been some sort of deal involving his parents; there must have been. That's when they would have taken him and changed him. Forever.
And now he is a feeder.
When the siren sounds, he has a few moments to rid himself of the grey overall and to kneel, naked, on the floor near the barrier. Then he closes his eyes and waits.
Soon the steam begins to pour in from vents near the top of the walls. It is heavy and, as it fills the room with its stifling whiteness, he struggles to breathe. His scrawny frame becomes hot and sweaty.
If he could stop himself sweating, he would. It is his greatest wish and his most persistent dream; a world without sweat. He thinks of it always as he kneels, shaking, sweat pouring from his cave-fish skin.
It drops onto the floor and runs down the gentle incline, through the narrow gap at the bottom of the barrier and into the water. In the middle of each bead is a tiny shape, silvery-black, wriggling and moving. Once in the water, the tiny shapes dart around, tasting their freedom. How he envies them.
When the steam stops, he remains kneeling for a while, waiting for the sweating to stop. The room soon grows cold and he collapses on his side, gasping and moaning. He crawls over to the barrier and gazes into the water as his thousands of 'children' swim around.
They grow before his eyes, becoming a few inches long within a matter of minutes. Only then do the sluice gates open and all the water drains away, taking the tiny fish with them. He always feels sorry to see them go. Even though he hates what he has become, he still feels they are his and that nobody else has a right to them.
He struggles to feel a sense of pride that he, along with hundreds of others, is providing sustenance for his people. But all he feels is pained and despairing and old before his time.
The bare wall faces him. Often he dreams that he wakes and the walls have all crumbled while he slept. Yet he never dreams what is beyond them - it is all just darkness, and an ominous rushing sound that seems to draw nearer and nearer yet never arrives.
High up near the top of the wall is a small door with a window set into it. It is way out of reach even if he stood on the table. The door is what they use if they ever need to enter this place.
Sometimes there is a small face at the window. She looks down at him as if she remembers him from somewhere else. Her eyes are filled with pain and pity. But then the siren always sounds and she is gone. He is never allowed to get as far as wondering who she is.
As he sits at his table, doing nothing, weighed down by despair, it comes to him. A single thought like a light coming on in a room too long in darkness.
He stands and looks down at the chair on which he has been sitting. His hands slide along the back and he tests its weight by lifting it from the floor. Even though the numbers are meaningless to him, the thing on the wall tells him the siren will sound soon, when the black marks move to a certain place.
He waits, hands gripping and back tensed ready. Then, as the siren sounds, he heaves the chair above his head and swings it down against the barrier. The material shatters and slides down under the surface of the water, becoming almost invisible.
Almost at once, he hears clattering sounds coming from behind the walls as feet scurry here and there.
As the steam begins to pour into the room, he climbs carefully down into the water. It is cold and it feels so odd to him, making him shiver as he wades forward. He is afraid of it, but not so afraid that he climbs back out. Better this than the life he has.
The steam is filling the room now but he is too cold to sweat. It feels wonderful: this is his dream.
He hears the door in the wall open and there are voices mingled with the steam. But the vapour cloaks him as he wades to the far wall.
His head slips below the water as he lies back, causing only a slight wave. Looking up through the liquid and the clearing steam, he can see the monotonous grey roof of his cell, broken only by two weak lights set into the ceiling.
He closes his eyes slowly and prepares to breathe in the darkness.