LINE of Duty returned to BBC One last week for its highly-anticipated fifth series, featuring Vicky McClure and Martin Compston.
Here’s all you need to know about what’s happened in the previous series…
What happened in Line of Duty season 1?
The first series debuted in 2012 and followed DC Kate Fleming, DS Steve Arnott and Superintendent Ted Hastings as they investigated recently named Officer of The Year DCI Tony Gates for corruption.
An innocent man gets killed after a counter-terrorist police unit raids the wrong flat.
Steve refuses to comply in a cover-up so gets transferred to AC-12, an anti-corruption squad which is lead by Ted.
The gang are called upon to focus their attentions on Tony who they suspect has been doing “laddering” – a technique in which different charges are placed on the same defendant to increase an officer’s number of successful cases.
Meanwhile Tony has offered advice to his girlfriend Jackie Laverty who claims to have hit a dog while drink driving home from a work party.
But it transpires that Jackie actually hit a person – her accountant who had unearthed that she had been laundering money for local mobster Tommy Hunter – not a dog as claimed.
Just when Tony was about to reveal what really happened, Jackie was murdered and Tommy was framed for the deed.
Tommy starts to blackmail Tony so he tries to track the mobster down, with AC-12 in hot pursuit.
Tony agrees to lead AC-12 to Tommy, allowing for his arrest before committing suicide.
But it’s not all over there! Viewers learn that DS Matthew ‘Dot’ Cottan had been Tommy’s inside man the whole time.
They gave him the codename of ‘The Caddy’ because he used to carry the mobsters golf kit as a youngster.
Matthew or ‘Dot’ told Tommy what to say to the police, leading him into witness protection.
What happened in Line of Duty season 2?
DI Lindsay Denton – as played by Keeley Hawes – lead the drama in this season.
The character was involved in a police convoy ambush which lead to the death of some colleagues as well as a member of public who was under witness protection.
But the anti-corruption unit become suspicious of DI Denton as it transpired that she was battling a crippling debt problem, and clock that she would have realised as the sole survivor she may be entitled to a big pay-off.
Arnott and Fleming from the previous series continue their hard work and focus their attentions on the shifty DI.
Fleming takes on the case after ending her affair with one of the deceased colleague’s husband’s.
While Arnott also embarks in a steamy relationship with sexy new colleague Georgia – until she meets a tragic fate.
And – perhaps unsurprisingly – the series ends with Lindsay Denton being found guilty as charged.
But it does come with a twist, her motive wasn’t so much financial as it was covering up a bad decision that lead to the death of four colleagues.
What happened in Line of Duty season 3?
The gang – Ted Hastings, Kate Fleming and Steve Arnott – turn their attentions to Roz Huntley (played by Thandie Newton) in this series.
They explore a potential miscarriage of justice when pressure to close a case resulted in the wrong man – Michael Farmer (played by Scott Reid) – getting locked up.
Is mother-of-two Roz responsible for an innocent man rotting behind bars?
And the series also saw officer Daniel Waldron investigated by AC-12 after a suspect was shot and killed.
But the first episode ends with the officer himself getting killed.
The unit uncovered a paedophile ring at Daniel’s old school involving some high-powered figures including Jimmy Saville.
It turned out that Daniel had been taking revenge on his previous abusers at the boys’ school.
But all the while, Dot was trying to stifle the case and stop it from coming out.
Series 2’s Lindsay also made a return after not being found guilty for conspiracy to murder.
And The Caddy became the subject of AC-12’s interest after two series of dodging justice.
Unfortunately he met his fate in a high-speed car chase as he tried to escape police officers.
What happened in Line of Duty season 4?
It was a busy series for AC-12 who got Roz Huntley, Jimmy Lakewell and one of the (no doubt many) balaclava men.
It also saw the exoneration of Ted Hastings, Michael Farmer and Hana Reznikova who were unfairly implicated in the conspiracy.
Kate, Steve and Ted unmasked Assistant Chief Constable Derek Hilton for his pivotal role in the series’ conspiracy.
Ted was convinced he was the mystery ‘H’ who was complying with powerful criminals, but the finale ended with Hilton dying.
The series ended with some loose ends that will no doubt be explored in the hotly-anticipated upcoming fifth series.
Are the plots based on true stories?
Yes- Some storylines are a case of art imitating life.
Speaking about these plot inspirations, showrunner Jed Mercurio told the Express, “Well, there are actually, really relevant examples in British legal history of Stefan Kiszko and you should look up who his solicitor was.
“It’s interesting – and the other one is Barry George, who convicted and then acquitted of the Jill Dando murder. So, there are actually, really relevant correlates in the British system.”
When is Line of Duty series five on BBC One?
The fifth season of Line Of Duty started on March 31, 2019 returns to BBC One for Episode two TONIGHT (April 7, 2019).
After series four concluded, the BBC announced Line Of Duty had been renewed for two more series – so we’ll be getting a series six too.
BBC director-general Tony Hall said: “I am very excited to say there’s not one but two more series of Line Of Duty. So hooray for AC-12!”
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What is Line Of Duty about?
Line Of Duty is a crime drama which first aired in 2012.
It follows the work of AC-12 a special unit charged with investigating corruption within the police force.
Jed Mercurio told the BBC: “I want to look at the personal lives of all the regulars in series five.
“They’ve taken a backseat in [series four] to Roz Huntley, so it would be good to explore that side of things a bit more.
“The regulars are definitely up for doing more.”