Line of Duty

Line of Duty follows D.S. Steve Arnott (Martin Compston), an authorised firearms officer, transferred to Anti-Corruption Unit 12 after refusing to agree to cover-up an unlawful shooting by his own team. At AC-12 Arnott is partnered with D.C. Kate Fleming (Vicky McClure), a highly-commended undercover officer with a keen investigative instinct. She is swiftly promoted to D.S. in series 4 and D.I. in series 5. They work under the supervision of Superintendent Ted Hastings (Adrian Dunbar), who is one of several Senior Investigating Officers (along with D.C.S. Patricia Carmichael (Anna Maxwell Martin) of AC-3 and those of AC-9) responsible for uncovering corruption within the police force. Throughout the series, AC-12 investigate seemingly disparate cases involving seemingly-corrupt police officers such as D.C.I. Tony Gates (Lennie James), D.I. Lindsay Denton (Keeley Hawes), Sergeant Danny Waldron (Daniel Mays), D.C.I. Roseanne Huntley (Thandie Newton) and undercover officer D.S. John Corbett (Stephen Graham). AC-12 realise the pervasive nature of corruption and the police's deep-rooted links to an organised crime group.

• Martin Compston as Detective Sergeant Steve Arnott, a detective sergeant assigned to AC-12, the anti-corruption unit within Central Police. Previously, he served as a counter-terrorism officer. He transferred after he refused to collude with his colleagues following the fatal shooting of an innocent man.
• Vicky McClure as Detective Inspector Kate Fleming, an undercover specialist. A consummate professional, Fleming is willing to investigate officers inside and outside AC-12. Initially a detective constable, she is promoted to detective sergeant at the end of the third series and to detective inspector following the fourth. Fleming is married with a son.
• Adrian Dunbar as Superintendent Ted Hastings, the senior investigating officer of AC-12. He recruited Arnott, Fleming and Cottan. Once a member of the Royal Ulster Constabulary, it is revealed that Hastings is a Freemason.
• Craig Parkinson as Detective Inspector Matthew "Dot" Cottan (series 1, 2 & 3), an AC-12 officer, initially introduced as a Sergeant on Tony Gates' TO-20 team. At the beginning of series 2, he is promoted to detective inspector and transferred to AC-9. He is seconded to AC-12 by Hastings. Cottan is revealed to be "The Caddy", working as a fixer for the organised crime group. He is killed at the close of the third series having escaped from AC-12 custody.
• Lennie James as Detective Chief Inspector Anthony "Tony" Gates (series 1), the head of the serious crime unit TO-20, Tony Gates is renowned for returning the best crime figures of any unit in Central Police. It is this reputation, however, that leads AC-12 to his team. Suspected of corruption, Gates faces an internal affairs investigation that adds further complications to his troubled home-life.
• Keeley Hawes as Detective Inspector Lindsay Denton (series 2 & 3), a silver commander who organises a convoy to transport a protected witness which is ambushed, resulting in the deaths of all the other police officers. As the only police survivor, Denton is arrested, charged with conspiracy to commit murder. She attempts to convince AC-12 of her innocence and regain her reputation, but eventually receives a life sentence. In series 3, Denton is granted an appeal, and is acquitted on the basis of an improper sexual relationship Arnott had with her while she was being investigated. She discovers crucial evidence pertaining to the Danny Waldron murder investigation and historical child sex abuse but after refusing to accept a bribe to conceal that evidence, she is murdered by "The Caddy".
• Daniel Mays as Sergeant Danny Waldron (series 3) is an Authorised Firearms Officer (A.F.O.). His armed response unit is investigated by AC-12, as a matter of routine following the shooting of a suspect. A deeper investigation is initiated when Arnott and Fleming discover the shooting may have been unlawful. Waldron is shot and killed by a colleague; his death results in an investigation into historic child sex abuse.
• Thandie Newton as Detective Chief Inspector Roseanne "Roz" Huntley (series 4), the senior investigating officer of Operation Trapdoor, and at the centre of an AC-12 investigation for mishandling evidence.
• Stephen Graham as Detective Sergeant John Corbett (series 5), Corbett is an undercover police officer who has been uncontactable for several months. He first appears as John Clayton, the gangleader of an organised crime group which hijacked a police convoy transporting seized drugs.
• Anna Maxwell Martin as Detective Chief Superintendent Patricia Carmichael (series 5), the senior investigating officer of AC-3, who is drafted in to review AC-12's handling of the Corbett investigation.

Line of Duty was created and written by Jed Mercurio. The first two series were produced by World Productions, on behalf of BBC Two. David Caffrey and Douglas Mackinnon directed series one. Mackinnon directed the first three episodes of series two and Daniel Nettheim directed the remaining three episodes. Mercurio produced series one and acted as executive producer for series two, with Peter Norris taking over as producer for series two.

In the United States, the first series was released on Hulu in August 2012 as an exclusive series, until Acorn TV picked up the streaming rights for its platform in 2018, which included the existing series and exclusive access to series five and later additions.[31][32] The first three series began airing on AMC starting 4 April 2020.[33][34]

• Line of Duty at BBC Programmes
• Line of Duty on IMDb
• Line of Duty at epguides.com
• Line of Duty at TV.com
• Line of Duty, scripts at BBC TV Drama archive