When a vagrant, the Walking Man, finds a dog wandering alone with a note attached to its collar saying 'help us', he's sure it's a desperate plea from someone in trouble and calls on Detective Inspector Jack Caffery to investigate. Caffery is reluctant to get involved - until the Walking Man promises new information regarding the childhood abduction of Caffery's brother in exchange for the detective's help. Meanwhile, a wealthy local family are fighting for their lives in their remote home ten miles away. Two men have tricked their way into the house and are holding the family to ransom. Yet as the captors' demands become increasingly bizarre and humiliating, it becomes clear that this is more than a random crime - it's a personal vendetta ...