Season 1 BBC Two , 2012 Watch now Steve Arnott is transferred to a Police Anti-Corruption Unit, where he finds his target is the city's top detective, Tony Gates. Season 2 BBC Two , 2014 Watch now AC-12 investigates the sole survivor of the attack on police convoy, escorting a civilian under a witness protection. Season 3 BBC Two , 2016 Watch now The new targets of the AC-12 investigation are Sgt. Danny Waldron and his team, who shoot dead a criminal, but cracks soon appear in their story. Are they covering up a murder? Meanwhile an old case develops a new angle. Season 4 BBC One , 2017 Watch now When DCI Roz Huntley captures a serial killer, the chief forensic investigator alerts AC-12 to a possible miscarriage of justice. Season 5 BBC One , 2019 Watch now AC-12 suspects corrupt cops are leaking information to a ruthless organized-crime boss who may be their most vicious adversary yet. Season 6 BBC One , 2021 Watch now
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