Breadcrumbs (S11E09)

Ellen Barker, a passionate follower of cold cases, is found dead, leaving behind a photo of Dan Griffin at her home. The murder investigation team interviews Griffin and uncovers that he and Ellen were friends. Leading the investigation is DCI Grace Mackie, a former classmate of Sasha Miller from their time at Hendon. Griffin believes that Ellen's final case may hold clues to her murder, prompting him to travel to Minchampton, where Sally Tunstall was killed 25 years earlier by a local named Dougie Haynes.