Marwood makes his vendetta personal - targeting Luther and those closest to him, raining destruction on everything he touches. Stark and Gray arrive just in time to hurry Mary to a secret place, but is her safety really Stark's priority, or is she just a pawn in his game to lure Luther to him?
Luther, bereft of friends and support, is left broken when he is accused of crimes he hasn't committed. But just as his situation seems hopeless, help arrives in the form of an unexpected ally. How can he stop Marwood becoming a public martyr, when he himself is on the run, forced to work outside the law?
Luther realises that Marwood's desire to avenge his wife won't be satisfied by punishing past offenders in this vigilante campaign - he also wants to punish his wife's murderer. Luther's private investigation leads him to discover that Marwood has kidnapped an innocent woman as leverage against the man who killed his wife.
Luther confronts Marwood, with disastrous consequences. Marwood, feeling that his control has slipped, becomes more unpredictable and dangerous. He wants Luther to suffer the way he has suffered. Suddenly Luther faces losing all that he holds dear, and is forced to make an impossible choice.