Still dishing for dirt on Luther the desperate Gray and Stark visit Mary, suggesting that Luther killed his wife. However Gray begins to sense that Stark is getting out of control in his desire for revenge and confides in Ripley. Meanwhile a young couple are saved from an attack by thugs by a mysterious man who shoots two of the assailants dead. Both of the dead pair are convicted killers and later another man who had been charged with murder is found hanged. Through a website Luther discovers the perpetrator to be Tom Marwood, taking revenge on killers freed by the system - such as the murderer of his wife Caitlin. He next abducts a paedophile Dennis Cochran, whom - following a public vote of approval on the Internet - he hangs. Luther and Ripley track him down but he steals Luther's phone and shoots Ripley before making his escape.