With Northern Ireland's Adrian Dunbar fronting the team of top cops, Line of Duty has been a massive hit.
So with anticipation building ahead of series 5, just what is on the cards?
The cast
The good news is, the core cast of Martin Compston, Vicky McClure and Adrian Dunbar will all be back for their roles as Detective Sergeant Steve Arnott, Detective Sergeant Kate Fleming, and Superintendent Ted Hastings.
Line of Duty won't end on a cliffhanger, says writer Jed Mercurio
As well as that, expect a star turn from Stephen Graham, who played the menacing 'Combo' in This is England, alongside Vicky McClure. Graham will play Balaclava Man, the mystery villain at the centre of series 4.
The storyline
When three police officers are shot dead during the hijack of a seized drugs transport, AC-12 move in to investigate possible police collusion.
Line of Duty cast behind-the-scenes in Belfast
Balaclava Man - aka John Corbett - is the ruthless leader of an organised crime group who hijack a seized drugs transport.
The AC-12 investigators suspect corrupt police officers are leaking information.
As the body count rises, AC-12 realise they’re facing their most vicious adversary yet.
Will this be the end?
While show creator Jed Mercurio said he thinks about ending the show before fans get bored, worry not - there's going to be at least one more series as a sixth season has already been commissioned for 2020.
Line Of Duty cast's Ted Hastings has his own drinking game reveals Adrian Dunbar
Where can you watch it?
On BBC One, Sunday March 31 at 9pm
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