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 hometown to look after him. But when he finally awakes from his coma, Mark believes that this Karin - who looks, acts, and sounds just like his sister - is really an identical impostor. 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.