Two-part fourth series of the BBC crime thriller starring Idris Elba as the brilliant but flawed murder detective John Luther. Following the murder of DS Ripley (Warren Brown), Luther takes a leave of absence from the force and retreats to the English countryside to lie low. But a visit from his former colleagues pulls him back to London where he is put on the case of a cannibalistic serial killer. Still haunted by past events, Luther must work with colleagues both old and new to bring another savage and intelligent criminal to justice. Dermot Crowley, Michael Smiley and Rose Leslie co-star.