Clinical psychologist Joseph O'Loughlin is trying to escape his past and come to terms with his Parkinson's by teaching at a university in the south-west. When the police need someone to talk to a woman threatening to jump off Clifton Suspension Bridge in Bristol, Jo reluctantly goes along. From there, his life and that of his family become inextricably tied to a vicious killer who murders his victims without laying a finger on them. Can Jo save the other women marked for death and, perhaps more interestingly, can his marriage survive the threat to his own family?