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.
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.