An inoffensive man is murdered in a seemingly motiveless attack. Detective Inspector Geraldine Steel and her team are baffled, until DNA from an apparent stranger is discovered on the victim's body.

Geraldine is not convinced the suspect is guilty. When a witness comes forward to offer the suspect an alibi, Geraldine lets him go. That night, a second murder is committed. The evidence points to the suspect who has just been released.

As Geraldine attempts to make sense of the suspect's complex history, he goes on the run. Even his wife appears to condemn him. Only Geraldine still doubts that he is to blame for the murders, but is she prompted by her own guilt for having released him to kill again?

As the story races towards a breathtaking twist, Geraldine is tormented by self-doubt, and struggles to focus all her attention on the case. Someone is lying and the police must uncover the truth before anyone else is killed...