Plot Synopsis

Like other police units, AC-12 investigates criminals--but the lawbreakers it catches are police officers working in the line of duty.

Season 1 followed one multi-stranded investigation over five hours, as Detective Sergeant Steve Arnott was transferred to AC-12, a fictional anti-corruption unit, after a mistaken shooting during a counter-terrorist operation. Alongside Detective Constable Kate Fleming, they are assigned to lead an investigation into the alleged corruption by a popular and successful officer, Detective Chief Inspector Tony Gates. While Gates cleverly manipulates his unit's figures, DS Arnott questions whether Gates's being made a scapegoat for a culture of institutionalized spin, or is guilty of darker corruption?

In Season 2, the ambush of a police convoy leads to the deaths of three police officers and critical injuries to a protected witness. As the sole surviving police officer, DI Denton is initially AC-12's most valuable witness. However, as their investigation becomes more complex and unsettling, suspicions begin to arise that Denton may not be so innocent after all. An addition to AC-12 is Detective Constable Georgia Trotman. Georgia is new to anti-corruption work and experiences ethical conflicts in investigating fellow officers. She also has impulse-control issues that lead to some uncomfortable situations in her professional relationships. Taking personal command of the overall investigation into the ambush is the ruthlessly ambitious Deputy Chief Constable Mike Dryden -- an officer with one or two skeletons hidden in his closet.

Season 3 opens with the fatal shooting of a criminal suspect by an armed response unit led by Sergeant Danny Waldron. Danny and his team claim they acted in self-defense, but AC-12, led by Superintendent Ted Hastings, gather evidence that suggests that this was a deliberate killing. Under interview, Danny confidently rebuts all of AC-12's accusations that he acted unlawfully, so DC Kate Fleming is sent undercover into Danny's team to find out more. Ingratiating herself to her new colleagues, Kate is quick to identify tensions and conflict between Danny and his team. But when Kate's own conduct comes under scrutiny, she finds herself sidelined from an armed drugs raid that goes very badly wrong.

Moving from BBC2 to BBC1, the fourth season of LINE OF DUTY begins with DCI Roz Huntley and her team in the thick of a career-defining case, Operation Trapdoor. Under intense pressure to catch the culprit and prove herself to her superiors, and facing conflict with her colleague, Forensic Coordinator Tim Ifield, it's not long before AC-12 decide to probe her handling of the investigation. A mother of two and wife to husband Nick, Roz will do anything to stop her life unravelling. Anything.

Season 5 follow a new case for AC-12 set nearly two years on from the crime drama's previous installment. When three police officers are shot dead during the hijack of a seized drugs transport, AC-12 move in to investigate possible police collusion. John Corbett is the ruthless leader of an Organized Crime Group (OCG), who hijack a seized drugs transport. AC-12 investigators Superintendent Ted Hastings, Detective Inspector Kate Fleming and Detective Sergeant Steve Arnott suspect corrupt police officers of leaking information. As the body count rises, AC-12 realize they're facing their most vicious adversary yet. The fifth season of LINE OF DUTY had its U.S. premiere on Monday, May 13, 2019 on Acorn TV.
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LINE OF DUTY had its linear television premiere on Saturday, April 4, 2020 at 10pm ET/PT on AMC.