Professor Edward Wilkinson has been murdered, and the chief suspect is his wife, Dr Helen Wilkinson. His death is just as she had imagined it so many times. He looks clam, asleep almost, for his eyes are closed; his hands are folded neatly on top of the fresh sheets. And yet something isn't right: in her fantasies there was never so much blood. Ruth Marks wants to protect Helen, to convince her she couldn't have killed her husband. But Helen has fantasised and planned and committed the crime so many times in her head she doesn't know what is real anymore. How can she tell the police she didn't murder her husband when she doesn't know for sure herself?
