He turned slowly around and studied the dim forms about him. No sound but for wind and rain. But there was a faint glimmer of light, no more than a pencil beam, from somewhere near the far end of the platform. As he reached it, he realised that it had to be from Ben's torch, and it was coming from the underpass to the other platform. Wary of slipping on the wet steps, he descended.

'They've probably found a telephone by now and called someone,' said Summerfield vaguely. 'There's really nothing to worry about.' He and Jane sat side by side in the pitchblack carriage, protected from moonlight by the hill behind them, as the art historian emptied the last of the wine into his glass. At least she had stopped crying now.

'I want to know why this is happening,' she said finally.

'That's like trying to explain the moon, or the course of people's lives.'

'It's all so random, and it shouldn't be. We've been telling each other stories all night, but they're not like life because they have plots. Nothing is left to chance. All this – there's no plot here, just a stupid accident, someone not doing their job properly.' She wiped her nose with a tissue. 'I don't want to be worried all my life. I'm tired of always thinking of others. When the children were ill, when my mother died, when Harold had his breakdown I was always the strong one. I had the answers and the energy to go on. It seems like there was never a moment in my life when I wasn't prepared to face disappointment. I feel like a fictional cliché, the academic's neurotic wife, and only I know that I'm not in someone else's story, that I'm real. Well, I don't want to be like that any more. I want someone else to take care of the worrying for a while. I want to go away somewhere warm and quiet. Where could I go, Peregrine?'

'I know a story about a special place,' he whispered.

'Is it real, though?'

'No, of course not. I don't know anything about real places.'

'But you must do. You're so much more practical than Harold.'

'Darling, I'm not real, any more than you are. In your heart you must know that.' And she knew he was right, for she remembered nothing before boarding the train.

Masters reached the bottom of the dripping tunnel and peered ahead. He could see nothing but the glare of the flashlight. 'Ben?' he called, and the reverberation of his voice was lost in the falling rain.

The torch lay in a shallow puddle. He picked it up and allowed the beam to cross the walls. There was no sign that anyone had been here. He continued through the underpass to the other side, but a rusted iron trellis barred the way to the opposite platform, so he made his way back.

When he reached the waiting room once more, he found it deserted. The fire burned low in the grate. Kallie's jacket was still lying across one of the benches, but the three students had disappeared as completely as if they had never existed. Masters was a rational man. He tried to remember their faces, but found he could no longer conjure their features in his mind. Shocked, he dropped down into the nearest seat and tried to understand what was happening.

They had been on a train, and the carriage had become separated, and they had walked to the station… Jane and Peregrine were still waiting for him, that much he remembered. He had just decided to walk back to them when he heard a distant pinging of the lines. Impossible, of course, but it sounded as though a train was coming. He ran out on to the platform and peered into the murky night as the sound grew louder.

Now he saw the bright, empty carriages swaying around the bend ahead, heard the squeal of brakes as the locomotive pulled into the station and came to a sudden stop before him. The green-painted carriage threw yellow rectangles of light on the platform. It bore the initials GWR on its doors. The compartments were separate and lined with colourful prints of British holiday resorts. The seats had anti-Macassars on their backs. The train was a flawless reproduction of one from his childhood, but why? And how? And surely it occupied the same line as their poor stalled carriage?

He had barely managed to climb inside and shut the door before it lurched off once more, running to its timetable as surely as Alice's white rabbit, and as Masters fell back into the seat he thought; this is a memory, an idealised moment from the past, correct in the details down to the curious acrid smell of such carriages and the itchy bristles of the seat, but not something that's really happening now – merely a culmination of fragments seen and experienced, not fact but fiction, someone else's fiction.

He pushed down the window and leaned from it, searching the track ahead. Where the stalled carriage should have been was nothing at all, no carriage, no track, no hills or sea, no night or day, just nothing.

And he thought; I've fallen asleep like one of my students, that's all it is. There's nothing to be afraid of. It's simply that I've lost the ability to tell reality and fantasy apart. Right now it seems I'm fictional but I know I'm real, for I have real memories. He thought hard and tried to recall something, a moment so exact and specific to his life that it would prove he was real, so that the fiction would break up around him like an unfinished short story. He tried to think of Jane and Peregrine, whom he knew had been having an affair for nearly two years, but could not conjure a single past memory from either of them. He thought about this evening, and the way it conformed to the most absurd conventions of a typical Hallowe'en short story; the stormy night, the train ride, the mystery destination, the tale-telling guests. Stay calm, he told himself, and remember, remember, he repeated as the train hurtled toward a stomach-dropping oblivion, remember something real and true, remember the last time you were truly happy.

And then a real moment came to him.

A dead, hot day in mid-July The air is countrified, dandelion spores rising gently on warm thermals, the lazy drone of a beetle alighting on dust-dulled hedge leaves. A suburban summertime, where the South London solstice settles in a sleepy yellow blanket over still front gardens.

Westerdale Road has its characters; the bad-tempered widow who appears in her doorway at the sound of a football being kicked against a wall, the deaf old couple whose pond freezes over every winter, so that they have to thaw their goldfish from a block of ice in a tin bath beside the fire. Some of the houses have Anderson shelters in their gardens, converted to tool-sheds in time of peace. Others still keep chickens, a distinctive sound and smell that excites the neighbourhood cats. Further along the street is a 'simple' man who sits on his front step smiling inanely in the bright sunlight.

Masters forced himself to remember, to stop himself from ceasing to exist. These weren't his memories, he realised with a shock, they belonged to someone else entirely. What were they doing in his head?

Many street names conjure pastoral imagery; 'Combedale Road', 'Mycenae Road', 'Westcombe Hill'. At noon the silent sunlight scorches the streets. Housewives stay deep within the little terraced houses, polishing sideboards, making jellies, listening to wirelesses in cool shadowed rooms. Their men are at work, mopping their brows in council offices, patrolling machine-room floors, filling out paperwork in dusty bank chambers. Their children are all at school, reciting their tables, catching beanbags, and in the break following lunch there is a special treat; the teacher unlocks a paddock behind the playground of Invicta Infants, and here is a haven from the hot concrete, a small square meadow of close-cropped emerald grass hemmed in with chicken-wire. Here we are allowed to lie on our stomachs reading comics, passing them between each other. It is peaceful, warm and quiet (the teachers do not tolerate the vulgarity of noise) and although we are in a suburban street, it feels like the heart of the countryside. And here is the heart of all remembered happiness.