Still plagued by the death of his ex-wife, Luther returns to work to face a surreal and nightmarish case of a masked murderer determined to enter into folklore. As the body count rises, Luther must use all his skills to stop the killer, at the same time trying to rescue an old acquaintance's daughter from the dangerous world of prostitution.

Luther must rescue Ripley, abducted by Cameron, in time to prevent Cameron's final murderous set piece. But Jenny's ruthless and vengeful boss is demanding compensation for stealing her protege. Luther is torn; will his visionary mind provide the team with the tools to save Ripley and the killer's intended victims, or will his focus be compromised?

As Luther's affection for Jenny grows, so does his determination to protect her and help her back on her feet. Baba, however, is determined to keep Luther on a tight leash. To add to Luther's difficulties, he is called in to investigate a man whose brutal and escalating murders seem to have no motive, leaving Jenny alone and vulnerable.

Luther's personal and professional life spirals out of control as he tries to cover up Toby's death and appease a suspicious Baba. He must also protect Jenny from any further harm. At work there's also a killer at large whose actions are ruled by his dice. How do you stop a man who sees life and death as a game and whose actions can't be predicted?

Luther investigates a the case of a fetishist who is murdering women which is similar to an unsolved case from the 1980s. The team attempt to catch the copycat killer, whose murderous spree has only just started.

Luther's date with Mary, and the promise of romance, is interrupted by the news of another murder. The killer has struck again - the number of victims is escalating fast.

In what looks like a gangland crime - two hoodies are shot at close range. But an un-connected crime sees Luther make a un-connected connection that might provide the real answer to what happened.

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?