As the hit BBC police drama continues, the internal affairs investigators of AC-12 face their most vicious adversary yet. Led by Superintendent Hastings (Adrian Dunbar, Blood), DI Kate Fleming (Vicky McClure, Broadchurch) and DS Steve Arnott (Martin Compston, The Great Train Robbery) probe the hijacking of a seized-drugs transport that left three officers dead. When they learn that an undercover officer is embedded in Corbett's (Stephen Graham) group, AC-12 comes closer than ever to discovering the identity of the ringleader within the police department—but what they find could tear their team apart. 6 episodes, 6 1/2 hrs, 2 DVDs. Mature content. Shipping October 2019.