Ophelia Marsh is studying English at Cambridge when the charismatic lecturer she has begun an affair with suddenly disappears. She tracks him down to his family home in Ireland, where she discovers that his wife, a famous author, has died in a fire. 

As her obsession with Roisin deepens, Ophelia begins to fear that Michael is not telling her the truth, and she feels haunted by signs of the dead woman wherever she goes. Meanwhile, Ruth's investigations in Cambridge reach Ireland with the arrival of a mysterious stranger, and Ophelia has to finally face up to whether she is losing her mind as Michael claims or, as she suspects, something more sinister is afoot