Every morning the river fog crept up the hill, pressed its damp grey face against Kiri's bedroom window and peered in at her, as if it had spent the whole night waiting to check that she was still there. She would lie under her blanket with the cartoon rockets on it and stare back, and the fog would stare at her, and neither of them would blink first.

At break she told Zofia about the fog, and Zofia said, 'You must miss the sunshine on your island.'

'Miss it?' said Kiri.

'You know. The beaches. The palm trees. All of that.'

'Probably,' said Kiri.

It wasn't probably, though. It wasn't anything. She had been two years old when the little plane took off, and the island lived in her head only as a photograph stuck to the fridge: a white beach, a green hill, and a baby who was apparently her, frowning at a coconut.

Zofia, who had sat beside Kiri in every lesson since they were seven, came from Poland. It was only two hours away by plane — less time than a maths exam, Zofia liked to point out. What she missed most was her grandmother's kitchen, where there were always dumplings cooling on a tray and nobody ever told you to wait until dinner.

Callum, Kiri's other best friend, came from Wales, which you could reach in a single afternoon on the train without ever showing a passport. What Callum missed most was the mountains. The hills around Brackwell, he said, were not proper hills at all, just fields that had sat up a bit.

Kiri's island was not on the globe in the school library. She had checked. Where it ought to have been there was only blue — a great deal of blue — and whenever she pointed to that empty patch of ocean, people smiled politely, as though she were pointing at nothing at all.

Brackwell Rovers had once been champions of the whole county league. Then, for a long and miserable stretch, they had finished bottom season after season, and now, according to the local paper, they were 'a side on the way back up'. Brackwell itself had travelled the same road. A hundred years ago its mills had woven more woollen blankets than any town in the north, and the streets had rumbled with carts from dawn to dusk. Later the mills shut one by one, their windows were boarded over, and the high street filled up with empty shops. But now there was a new tram line to the city, artists had set up studios in the old mill buildings, and families were arriving from all over, looking for cheaper houses and a bit more sky.

On her first day at secondary school, the PE teacher had read Kiri's name off the register, looked up and beamed. 'An island girl! You'll be our star swimmer, then.' Kiri sank like a stone in the school pool, and on the Year 7 trip she was seasick on the ferry, both ways.

Kiri liked machines.

More than liked them. She loved the insides of them — the cogs and springs and tiny screws that nobody else ever bothered to look at. Whenever something in the house broke, she carried it upstairs to her desk, which she called 'the Hospital', and laid it out on an old towel. Sometimes it came back better than before. Sometimes it did not come back at all, and its pieces went into a biscuit tin under her bed, which she called 'the Graveyard', and there they stayed, rattling whenever anyone hoovered.

But plenty of her patients recovered. Last winter she had rescued Mum's old radio, which had been silent for three years, and when it suddenly crackled into life halfway through the shipping forecast, Gordon had lowered his newspaper and said, 'Well, I never. Did you do that?' Mum had laughed and said, 'Of course she did,' and Kiri had felt about ten feet tall.

Oiling a bike chain was honestly the most satisfying job in the universe. If you did it properly, one drop on every single link, the chain went from grinding and squeaking to whispering round like it was brand new, and if you gave the pedal a spin afterwards, it just kept going and going all by itself. Way better than telly. Way better than anything.

'You'll be an engineer one day, you will,' Mum often said, in her gentlest, most encouraging voice. Kiri had noticed, though, that Mum had wound a thick bandage of sticky tape round the kettle lead that Kiri had mended for her, and that when the doorbell stopped ringing, it was a real electrician who came to fix it.

Mr Okafor, who ran the after-school science club, had told them all on the very first day, 'Remember, the sky's the limit.' Then he had glanced up at the brown damp patch spreading across the ceiling of the lab and added, 'Within the school budget, obviously.'

Glossary
mill: a factory where wool or cotton is spun into thread or woven into cloth
county league: a football competition between teams from the same area
shipping forecast: a weather report for sailors, read out on the radio