When Claire comes to in hospital after a minor traffic accident, she finds that her behaviour seems to have altered dramatically. She also finds that she is the focus of attention of a mysterious stranger who commands her sexually in a way she has never experienced before.As she recovers her leads her into more and more extreme encounters that she finds herself taking more and more pleasure in. But then she goes on holiday with her husband and he disappears just as the mysterious 'X' makes ever more stern calls on her body.