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.