A freezing room in a student house, a sagging mattress on the floor, and two people, one nineteen, the other twenty, kissing passionately. All night.

It is to this scene that, twenty years later, Rosy, the narrator of Julie Myerson's astonishing new novel, returns obsessively. She has just lost a child in a terrible, careless accident, and Tom, her partner, has taken her to Paris to forget about things, to start again.

It has snowed in the night and, waking at dawn, Rosy decides to go for a walk. At the hotel desk there's a note for her: 'I'm waiting for you X.' And he is, sitting in the corner of a cafe she enters almost at random. They talk. He touches her. She turns away and when she looks again he is gone.

Was he there? Had she dreamed him? And why, when he emails her out of the blue two days later, does he write as though they haven't met for twenty years?