Contains spoilers for this episode.
Davis brings his girlfriend Pia to his Scottish hometown while planning a small nature documentary. They stay with his mother Janet and hear about the murders that ruined the area's tourist trade. Local man Iain Adair was blamed for killing several people, including Davis's father, a police officer. Pia sees a more compelling film in that story, and Davis reluctantly agrees to investigate with help from his friend Stuart.
A producer wants a fresh discovery rather than a retelling. The filmmakers enter Adair's abandoned home and record its basement using old videotapes from Janet's collection. After a car accident puts Davis in hospital, Pia examines a recording alone. It contains footage of Janet and Davis's father participating in the torture. Pia realises that the welcoming household belongs to two of the killers, with the surviving one preparing dinner nearby.
Unable to get a signal, Pia flees into the darkness. Janet follows, but Pia falls while crossing water and dies from her injury. Janet returns home, gathers evidence for Davis and kills herself. The completed documentary exposes how his father killed Adair and staged his own wound to conceal the wider crime. Stuart's pub fills with visitors, and the film wins an award. Davis sits alone afterward with Janet's note dedicating the evidence to his film, having gained professional success through the destruction of his family and the loss of Pia.