The dust was bad on Sunday. By Tuesday, they were all coughing. They’d known the storm was coming for a week, but there wasn’t much they could do to be ready for it. Preparation was a lost art because it presumed that a future was inevitable.

In the decay of the bottom layers of the Old City, they seemed to be going backward in time, into some primordial grime soup. The brew had begun when the bots had broken the laws made by man and began to gnaw away at it. Funny how the DNA folds designed to be medicinal - to cure cancer, obesity, heart disease – could have mutated and begun to unravel all life. Cities like this one would fall eventually, but genetics allowed families like Cally’s to survive, and ingenuity and circumstance allowed the tower folk to eke out a life that was enviable, in relative terms.

Cally and his sisters could wet hankerchiefs and tie them around their faces, but water was scarce, so the dust wiggled under the folds of cloth and into noses and lungs. They could shut the doors and windows and board them up, but the dust was persistent in its begging and, wolf-like, battered down any attempts at resistance. It swept in from the deserts that surrounded the Old City and nibbled and chewed a little more off it’s edges.

Once it had finished pulling apart the forests, and there was nothing to hold together the earth, the dust became part of everyday life. Nothing held it at bay. It settled into thirsty pores of skin and choked the life out of those that lived there. If you were blessed with a healthy set of lungs and a kick-ass immune system, you might last a little longer, but Cally was approached twenty five and knew his days were numbered. He tried to hide it, but when he coughed, his sisters looked at him and looked away quickly. His one intact lung was struggling for air, but, he reasoned, he could still breathe. Each breath was a blessing. As long as he could inhale and keep his sisters going, one rotten lung didn’t matter. It was better than no lung at all.

The newspaper had arrived this morning, and he eyed it cautiously where it sat on the upturned packing crate. The tower folk used to send pigeons, once. As a boy Cally remembers his mother unravelling a scrap of paper from the leg of a bird, reading it and throwing it into the small fire that was heating water his father’s medicinal tea. She wouldn’t tell the children what it said. Instead she made up a story of princesses and towers and yellow hair, which was quite inconceivable in a city where all hair was matted with dust, and sunshine was a distant memory. Cally remembered being horrified at his mother snapping the neck of the bird with one determined flick of her wrists. Yet as the creature roasted in the weakened flames fed by books, and the sweet smell of sustenance filled the hovels, he forgot the joy he felt in seeing such winged beauty. His belly would win over the feeling that the bird's life was sacred. He could almost hear the snapping bones of vertebrae all over the city.

After that feast, there would be no more carrier pigeons sent from towers.

He wondered where they got the printing press from. Proper industry in the Old Town had long ceased, with little workers left to feed it, and the pathways out of the city were impassable. They had been for a decade. Most of the residents had re-conditioned devices at best, with shattered screens and batteries that would last minutes rather than days, and had taken to more old fashioned methods of getting word about the city, but somewhere, up on high, a newspaper was printed to pass amongst the folk below.

The newspaper had already been passed from hand to hand, and they would pass it to the next family so that they could read the propaganda there too. The lies said that life could be better, if only they all worked hard. They needed to give of themselves so their families might prosper.

The language of the Old Town was all about sacrifice. The first words the Cally remembered his younger sister saying was ‘I’ll give up everything for you, brother!’. He’d laughed and ruffled her hair, but to be honest, he had known even then that they’d all be forced to give up something and get not much in return for it. Except, perhaps, love.

After the pigeons, it was quite likely that the upper folk had gotten a little more inventive about how they were send out their requests. When you need a lung or a liver, inventiveness was necessary. In whatever form the missives took, those below the towers would rush to answer. They all hoped for the chance for the clearer air in the skies above. Sometimes the promise would be for a room with a good and proper air conditioner to filter out some of the damn dust, or a job as a gardener in the glass ceiling observatories. No one really knew. If you entered the basement and worked your way to the glass elevators, you weren’t ever coming back. No-one ever did. Who would ever choose to return to the squalor in the city below?

‘Cally-scally, what’s a-bothering you?’ His sister looked at him quizzically, wondering why his interest seemed so glued to the paper. She was eighteen and her eyes were already crow footed. He wondered about the crows, and when they’d left the city. He imagined it as around the same time as his parents had died, but he wasn’t sure if he had merely tied the two events in his head because in the books they’d left behind, long since used as tinder to light fires to cook pigeons and rats, black birds were always associated with death.

‘Look!’ he said. The advertisement was on the front page, and he wondered how she’d missed it.

‘If you have the credits - we have the time travel!’

The picture beneath showed a time-box, and a little girl inside it with her face pressed to the glass. She was washed clean of the grime of old town and wore a bright blue dress, as blue as the sky they’d not seen since they were small.

In the time-boxes, they could see any thing they wished, in any time zone they desired. It was the habit of his father to give credits to his children so they could time travel on their coming of age day. On his son Cally’s age day, he had given his left hand. He only needed his right, he argued. His mother had not spoken to him for weeks, but had eventually got used to the hook that was quite effective in scooping and skewering the mice that darted under the floorboards.

Cally had chosen to see vultures on the steppes of Tibet in the late twentieth century. His sisters were appalled as he described the bodies of the dead left out for funeral rites, but he was happy with his time choice. He had drunk in the blue blueness of the skies touched by the tips of the Himalaya, and watched the vultures feed before they began soaring upward, riding the currents to the highest mountains. How he wished to fly skyward, like those birds.

His sisters wondered why he hadn’t travelled to some better memory, like when their father brought them home apples for dinner. How they could remember the crisp sweetness of that longed for fruit, and the smile on their mother’s face! What they wpuld give to travel back to those sweet times! He made them promise that if they had enough credit and the time boxes invited them again, they would travel somewhere with vast skies. The Sahara, maybe, under a whirl of stars.

‘I’ll give blood again!’ his sister cried. Suddenly the time box in the advertisement was everything, all coughing and woes forgotten.

‘Can you afford to?’ Her face was white, like the ash that sometimes rained down on them when the storms came from the north. He didn’t want his favourite sibling to waste away. Two years ago they’d lost their brother, because they’d asked for kidney that month, and he’d stupidly forgotten he’d already given one. The doctor who’d extracted it didn’t think to check for the scar on the other side.

Johnno's kidneys hadn't gone completely to waste. He had never time travelled to see the blueness of wild oceans like he wanted to, but his body parts would rejuvenate those that were lucky to be born in the tower blocks. His father’s hand, too, he supposed, was transplanted onto one of the rich who’d needed a better limb than what he’d been born with. How lucky the tower folk were to have the surgeons and the technology to keep them so vital, so alive!

Of course they need the donations to do it, because the nano-bots hadn’t worked at all, despite the proclamations that they would cure all disease, and despite the billions poured into their research and development. The bots had rebelled and destroyed the very world in which their makers sought immortality. Those below would sometimes bitterly call the donations blood-sacrifices or red trades. If you wanted life, they would declare, you had to pay with life.

Cally thought that the red trades weren’t so bad. They bought you credit, and the credit would sustain your family for another day, a week, a year. Blood trades could buy you bread and sometimes milk, or if it was a good year, perhaps some greens and once, Cally remembered, a small bunch of wizened grapes. Bigger red trades would buy you luxuries, like escapes into the time boxes. Looking into his sisters faces was confirmation enough that such respite could make a difference to their happiness. And his sisters happiness was his own.

Cally’s youngest sister was quiet, knowing she could little afford to donate again this month, let alone afford minutes in a time-box. Yet to Cally, this was unfair. She was the only one who hadn’t been in one and it seemed unfair to him that his favourite sister shouldn’t see the memory of the sky. It was small things like that that sustained a soul, down here in the darkness and dust that swallowed all dreams and hope.

It only took Cally once in a time box to be in love with them forever, like a boy in the long-gone past who was in love with aeroplanes or steam trains. He told the story over and over again to his sisters. You entered the approximate decade (the dial didn’t allow for greater specificity) and then swipe your fingers around to move a map in space, turning it around in your fingers like a real globe until you landed on the place you wanted to go. And there it was – a remnant of time easing out into the visual field before you. You could see it through the glass, smell and taste it through the comms, but not actually step out onto the vista. That didn’t matter. It didn’t even matter than they couldn’t stay there, or change the environment to butterfly effect the future in which they all now suffered. What mattered is that they had seen real life, and real birds, and real sunshine, and a real sky. What mattered was that it had existed once. That was enough for them all to dream of minutes in time boxes, paid for with credit they could bare afford.

Cally picked up the advertisement again. His sister clutched his one remaining hand. His single eye stared at her lovingly.

‘It’s okay,’ he smiled. ‘It’s your birthday, and I still can buy credit.’