On a winter night on a remote road in Nebraska, Mark Schluter's truck turns over in a near fatal accident. His sister, Karin, returns reluctantly to their home town to look after him. But when he finally awakes from his coma, Mark believes that Karin - who looks, acts and sounds just like his sister - is really an identical imposter.

Shattered by her brother's refusal to recognise her, Karin contacts Dr Gerald Weber, famous for his case studies describing the infinitely bizarre worlds of brain disorder. But what Weber discovers in Mark begins to undermine even his own sense of self.

Meanwhile Mark, armed only with a note left by an anonymous witness, attempts to learn what happened on the night of his accident. The truth of that evening will change the lives of all three beyond recognition.

Winner of the National Book Award for Fiction.