Usually, in police dramas, internal affairs investigators are portrayed as the enemy – cold, heartless traitors to the devoted, hardworking cops trying to solve cases and make convictions. The Line of Duty BBC TV series on Hulu turns this game around. The show’s stars are all in AC-12, a British equivalent of internal affairs, and they spend their time investigating fellow cops that may be less than honest. It’s an effective idea for a cop show, a genre where new ideas are often hard to come by.

DS Steve Arnott (Martin Compston) is the first of the three lead investigators we meet. He was in a different unit and transferred to AC-12 – essentially as punishment – after a raid went bad, and a civilian was killed. His new boss is Superintendent Ted Hastings, played by Adrian Dunbar, who initially seems to fit all of our preconceptions about internal affairs. Arnott is not happy about his new post, particularly when he is assigned to investigate DCI Tony Gates (Lennie James), the new Officer of the Year.

vicky mcclure line of duty bbc

DC Kate Fleming

The third member of the anti-corruption team, DC Kate Fleming, played by Vicky McClure, is put in place undercover to investigate Gates’ unit  from within. Gates has an exceptionally high case clearance rate, and though it appears Hastings has targeted him without any real cause, things soon begin to change.

Line of Duty series creator Jed Mercurio has wisely written complexity into this BBC TV show, with several shades of gray on both sides of the investigation. Are the cops under suspicion really corrupt or just victims of circumstance, perhaps making a single poor decision along the way? The AC-12 unit sometimes seems too eager, never giving fellow police the benefit of the doubt. At the same time, they rarely receive cooperation – to say the least – from other units; their job is not an easy one.

The first Line of Duty season follows the Gates case, which is, of course, more than it originally seems to be, mixing the personal and professional lives of the officers. Line of Duty season 2 tracks a new case, which again starts with a botched operation. There are plenty of secrets and a troubled Deputy Inspector. Our suspicions about the extent of her guilt rise and fall in the early episodes, and the fairness of AC-12 is called into question.

Line of Duty season 1 has five, one-hour episodes; season 2 has six. The series first aired on BBC Two in 2012; the second season followed in 2014. Two more seasons have been approved for production; series 3 may air late in 2015. Line of Duty has received both popular and critical acclaim. If you watch TV online via Hulu or Netflix, Line of Duty is one of the better BBC police dramas of recent years.