DCI John Luther returns to work after the traumatic arrest of a serial killer, and his first case is to investigate the seemingly perfect murder of a former child genius's parents. However, everything is not as it first seems, and when Luther is unable to find evidence to convict, he becomes embroiled in a battle of wits with the suspect - who has set her sights on him and his estranged wife.

DCI Luther finds himself on the trail of Satanic occult killer, Lucien Burgess, who was previously accused of kidnap and murder but escaped charges due to police misconduct. However, with a young mother's life at stake, Luther must now use all his skills to build an airtight case and seeks out guidance from Alice. Meanwhile, Mark is beaten up by a gang of young girls, and Zoe discovers her feelings for Luther remain strong even after she doubts his integrity.