When a vagrant - the Walking Man - finds a dog wandering alone with the words “HELP US” written on its collar, he’s sure it’s a desperate plea from someone in trouble and calls on Detective Inspector Jack Caffery to investigate. Caffery has no idea who or what he is searching for, but one thing he is sure of: it's a race against time. Meanwhile, the Anchor-Ferrers, 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 for 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.