The story begins in the middle of a tense situation as we are greeted with O'Loughlin sitting on a London rooftop trying to talk down a young suicidal cancer patient. We are immediately given a sense of his capabilities as a psychologist not to mention the hint of roguishness that makes him an endearing character. He seems to have a perfect life with a beautiful wife and daughter and a successful practice. The only dark cloud hanging over the vital 42 year old is that he has been recently diagnosed with Parkinson's disease.
As well as working in his day to day practice, O'Loughlin is the kind of man who gives up his time to counsel prostitutes in ways in which they might be able to work more safely. It's while talking at one of these gatherings that he meets Detective Inspector Vincent Ruiz, who has walked in with a picture of a murdered woman hoping to get her identified by one of the attendees. In the course of their confrontation, Ruiz decides that O'Loughlin's keen eye for detail and professional credits might be useful in providing some insights into the dead woman, so he invites him into the investigation as a consultant.
The woman had been found in a shallow grave next to a London canal. She has multiple stab wounds over her body, all of them self-inflicted plus many old wounds on her arms and thighs indicating that she was a self-mutilator