As the investigation takes a shocking turn, secrets rise to the surface. When Andrew was living in Edinburgh, a strange turn of events brought him face to face with an old acquaintance, whose deeply corrosive influence becomes clear. Meanwhile, the tragic recent history of Laura's family helps explain the deep bond she and Katy share, as well as the lengths Laura will go to for those she loves. Will her past catch up with her, just as Andrew's did? Thriller, starring Ioan Gruffudd and Joanne Froggatt.