After investigative journalist Lisa Wallace publishes an article about her mother's murder, girls start to disappear, leading her and Detective David Burkely to search for them across Ireland while the killer taunts Lisa.

Lisa's article criticising the Gardaí for not acting on Amy's disappearance is leaked; David and Detective Brennan chase a lead in Castlemoy; impatient with the police's pace, Lisa risks her life to uncover what that lead is hiding.

David tries to get a statement from Teresa and a confession from Bulger; Lisa investigates Bulger; Susan pleads for information on an anonymous informant from the Gardaí.

Lisa has to choose who to save between Susan and Mandy; Chris learns new information that takes Lisa to a strange address, where she discovers incriminating information.

David and Brennan target Gough as the potential killer and Lisa tries to connect him to the kidnappings; Gill threatens to blackmail David if he continues his investigation of Gough; Lisa receives a call about her father from the hospital.

The investigation is halted; David confronts Gardaí's top officials to expose Gill and Gough, but he finds no support; Lisa and Brennan follow a lead on the killer, investigating an abandoned slaughterhouse.