A middle-aged woman named Martha is brutally stabbed to death in the local park. Her husband, who did not report her missing, secretly pays a prostitute to give him an alibi to avoid becoming a suspect. Then the prostitute's body is discovered, strangled, and the police think they might be dealing with a brutal killer who will stop at nothing to cover his tracks. While they are hunting for evidence, another prostitute is murdered. With very little to tie the three murders to one another, DS Ian Peterson struggles to make sense of the case and find the elusive killer before he strikes again.