A young woman is moving dangerously close to the edge of the rock face, pushing a stroller with a child strapped in it towards the steep drop. She has blood on her clothes. Is she a victim or a would-be killer? Detective Inspector Joanna Piercy takes on the case when a walker discovers the pair, but the young woman is mute. Is she traumatized or unwilling to speak? Was she about to commit a terrible crime? As the questions mount, forensic psychiatrist Dr Claire Roget is called in to help. Can she persuade the woman to talk? Joanna desperately needs a breakthrough. But when it comes, her investigation takes a shocking turn.