Like other police units, AC-12 catches criminals-but the offenders it investigates are fellow officers. When a police convoy is ambushed, leaving three cops dead and a protected witness seriously injured, AC-12 focuses its attention on the one officer who managed to escape the attack unscathed: Detective Inspector Lindsay Denton (Keeley Hawes, Spooks, Ashes to Ashes).

Under the direction of Superintendent Ted Hastings (Adrian Dunbar, Ashes to Ashes), partners Detective Sergeant Steve Arnott (Martin Compston, The Great Train Robbery, Ice Cream Girls) and Detective Constable Kate Fleming (Vicky McClure, This is England, Broadchurch) begin to put the pieces of the case together. Their investigation takes them ever higher up the police hierarchy, all the way to the top ranks of the force. Hailed as "the most enjoyable series the BBC has produced in a long time" (Sunday Times, U.K.), the thriller is "back with a bang" (Daily Telegraph, U.K.) in this six-part second series. 2 DVDs, approx. 369 minutes, SDH.