Kate used to be good at recognising people. So good, she worked for the police, identifying criminals in crowds of thousands. But six months ago, a devastating car accident led to a brain injury. Now the woman who never forgot a face can barely recognise herself in the mirror.At least she has Rob. Young, rich, handsome and successful, Rob runs a tech company on the idyllic Cornish coast. Kate met him just after her accident, and he nursed her back to health. When she's with him, in his luxury modernist house, the nightmares of the accident fade, and she feels safe and loved.Until, one day, she looks at Rob anew. And knows, with absolute certainty, that the man before her has been replaced by an impostor.Is Rob who he says he is? Or is it all in Kate's damaged mind?