We open to find DCI John Luther has, for the first time in a long time, found peace with himself. He has a new home and a weary contentment which sits well on his troubled shoulders. It’s not long, however, before his equilibrium is destroyed and Luther finds himself under more pressure than ever before. A copycat killer is on the loose but Schenk wants Luther on the case of a murdered internet troll. Trying to juggle two investigations soon puts a strain on the friendship between Luther and his loyal partner, Ripley. Meanwhile, Luther has a new nemesis to deal with. DSU George Stark has a file full of incriminating evidence and an unlikely ally in Erin Gray. Together they are determined to bring Luther down. There’s hope around the corner, however, when a chance encounter means that Luther might just be on the verge of finding love. Then a vigilante killer embarks on a crusade to punish criminals, and Luther is forced to confront his own sense of justice and the moral order. Meanwhile George Stark’s using dirty tactics and the campaign within the force to bring Luther down knows no bounds. When the vigilante killer starts threatening to destroy everything he holds dear, there’s only one person Luther can rely on to help…