Line of Duty series 1-3 recap: everything you need to know before the BBC drama returns
Get up to speed on the first three series of the BBC's thrilling cop series ahead of the new episodes
Line of Duty is back, and if you've been following the drama from the beginning you will know that is a very good thing.
Even though each series of the BBC's thrilling cop show has focused on a different anti-corruption case, the key cast of characters has remained the same throughout, and old investigations are never quite forgotten.
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Series four begins with something of a fresh start for anti-corruption unit AC-12 after the dramatic conclusion to series three, but that doesn't mean you should dive into the first episode without a good briefing.
Here is everything you need to know ahead of series four. Obviously, MAJOR spoilers follow for the first three series. If you haven't watched them yet, the first two are available on Netflix, and the third is available for free on BBC iPlayer.
What is AC-12?
AC-12 is the name of the dedicated unit responsible for investigating police corruption – basically rooting out the bad apples in the Force.
DSI Ted Hastings (Adrian Dunbar, centre) is in charge of the unit, assisted by DS Steve Arnott (Martin Compston, left) and DS Kate Fleming (Vicky McClure, right).
Arnott caught the eye of Hastings in series one, when as a firearms officer he blew the whistle on a botched operation. He was assigned to AC-12, working alongside undercover officer Fleming. They've been an effective team ever since.
What happened in Line of Duty series one?
AC-12 was tasked with investigating high-flying copper Tony Gates (Lennie James), recently named Officer of the Year.
Gates had agreed to help his lover Jackie when she told him she'd hit a dog while drink-driving. In actual fact, it transpired she had hit her own accountant, after he discovered she was laundering money for local gangster Tommy Hunter.
Just when Gates was about to reveal all, Jackie was murdered and Hunter framed Gates for the killing. The gangster blackmailed Gates, saying he would hand the fabricated evidence over to the police unless he did as he was told.
In desperation, Gates tried to track down his blackmailer alone, with AC-12 in hot pursuit. With no way out, he agreed to lead AC-12 to Tommy, securing vital evidence that led to Hunter's arrest before committing suicide.
And that would be that... if it weren't for 'The Caddy'. At the end of the series, viewers learned that DS Matthew "Dot" Cottan (Craig Parkinson), one of Gates's subordinates, had been Tommy Hunter's inside man all along. He was codenamed 'The Caddy' as he used to carry Tommy's golf bags as a kid.
Dot told Hunter what to say to the police, getting him into a witness protection programme. Which brings us to series two.
