Next weekend Line Of Duty returns for a sixth series —and not a moment too soon. The hugely popular police drama is a must-watch for armchair sleuths. At the heart of the action is AC-12, the anti-corruption squad headed by Superintendent Ted Hastings (Adrian Dunbar) and his two trusty sidekicks, Detective Inspector Kate Fleming (Vicky McClure) and Detective Sergeant Steve Arnott (Martin Compston). 'My department carries out its duties to the letter of the law,' says Hastings. Yet, week after week, viewers are lured into a dark and complex world of police-on-police crime that is sometimes shocking and often confusing.