An elderly academic on his way home from the cinema is accosted by a homeless woman. She tells him her name is Laura. So begins a nightmarish journey for Gerald, a historian forced to confront the mystery of his own past, and to ask himself if he has lived a good life or even a decent one.

In the course of this very funny, sometimes disturbing and often moving novel, suppressed memories return to haunt him. There is the matter of the bag of farthings, stolen when he was just a small boy. And the question of therole he played in a family tragedy. Above all he has to assess the harm he may have done in a long-forgotten love affair.

Even those close to him suddenly appear unfathomable. How well does he really know his friend Terence, an apparently unworldly physics professor who inspired Gerald's course on quantum history, or the vivacious, recently widowed Judith, his sister-in-law? And what about Abby, to whom he has been married the whole of his adult life? He seems to understand her as little as he understands himself.

The problem with exploring the past, Gerald begins to see, is that there are an infinite number of ways to travel through it.