Idris Elba returns as John Luther, the near-genius detective waging his own war on crime. This series sees a twisted fetishist targeting young women in London. Luther is convinced the man will strike again, but when the detective is ordered to investigate another case, the chances of catching the killer start to fall. But Luther's biggest threat could be closer to home, when it emerges that his own colleagues are willing to break every rule in the book to bring him down...