All the episodes from the first, second and third series of the British crime drama starring Martin Compston and Vicky McClure. In the first series, as punishment for a previous failure, Detective Sergeant Steve Arnott (Compston) is transferred to AC-12, a unit assigned to investigate corruption within the police force. Working with Detective Constable Kate Fleming (McClure), Arnott quickly finds himself immersed in a case involving Detective Chief Inspector Tony Gates (Lennie James). With Gates a slippery and resourceful adversary, the pair will have to keep their wits about them if they are to crack the case. In the second series, an ambush of a police convoy sparks alarm when three officers are killed and a witness in protective custody is seriously injured. With only one survivor, Detective Inspector Lindsay Denton (Keeley Hawes), department AC-12 is brought in to solve the case. In the third series, Sergeant Danny Waldron (Daniel Mays) and his team are assigned the case of a suspected gang member who has been arrested on suspicion of plotting a gangland murder. When Waldron shoots the suspect in cold blood and stages the scene to look like self-defence, DI Denton brings in Waldron for questioning.