Line Of Duty will conclude on Thursday with fictional anti-corruption police unit AC-12 on the hunt for bent officers, past and present.
The net is closing in, but will AC-12 get to the truth at last?
Line Of Duty's third series has been a phenomenal success for BBC Two. The gritty cop drama, which featured Daniel Mays as Sergeant Danny Waldron, has frequently averaged more than 3 million viewers in the overnight ratings.
Last week's penultimate instalment concluded with the shocking death of DI Lindsay Denton, a magnificent portrayal by The Durrells' Keeley Hawes, and drew 3.4 million.
Consolidated figures, which include viewing on the night of transmission and people who recorded the show and watched it in the subsequent seven days, have so far seen the BBC Two series well over the 5 million mark.
Series four must surely be a formality.
As we prepare to bid a fond farewell to one of the best British dramas of 2016, here are five reasons we'll miss Line Of Duty.
1. Three is the magic number
Martin Compston, Vicky McClure and Adrian Dunbar continued to anchor the series with their top-notch portrayals of Detective Sergeant Steve Arnott, Detective Constable Kate Fleming and Superintendent Ted Hastings respectively.
Good cop and bad cop can be over-familiar television archetypes, but in the world of Line Of Duty they're far from being cartoonish stereotypes.
This is a collection of utterly believable, but flawed, characters. And they're all convincingly portrayed by terrific actors.
2. DI Lindsay Denton ruled
What is there to say about Keeley Hawes's acclaimed performance as Detective Inspector Lindsay Denton that wasn't said in series two? She made the 2014 incarnation of Line Of Duty one of BBC Two's most watched shows that year thanks to her searing portrayal of the morally ambiguous cop.
And for series three? Let's just say social media exploded when DI Denton made her first shock appearance. In addition, the jaws of millions of fans dropped to Australia when Denton was killed off.
She had become a bona fide cult figure, the woman we loved to hate and hated to love. That puts her in the company of the likes of Dallas's great villain JR Ewing or EastEnders' Grant Mitchell - and you can't do better than that.
3. For daring to use Savile
Line Of Duty writer Jed Mercurio dared to utilise the disgraced Jimmy Savile for his storyline dealing with allegations of child sexual abuse and a cover-up aided and abetted by bent coppers.
A photo was mocked up in which Savile was shown shaking hands with the drama's fellow paedophiles.
It was a gasp-out-loud moment and a huge talking point. But it also underlined Jed's commitment to telling his story, even if it made some uncomfortable.
4. For nail-biting tension
Kudos to writer Jed for crafting a drama which continues to be so much more than just a story of corrupt or amoral cops. From a seemingly simple premise, we've watched over two nail-biting series as those who are sworn to uphold the law invariably break it and lose their moral centre.
Each series has upped the stakes involved and built the tension to an unbearable level, wrong-footing fans and critics alike with more twists than Spaghetti Junction.
Who knew we'd lose Sergeant Danny Waldron in the first episode? Who could have predicted everything that happened to Denton? Did anyone bet on armed response officer Rod Kennedy (Will Mellor) meeting a sticky end so soon? The list goes on and on.
5. The interviews are awesome
A consistent Line Of Duty feature has been the blisteringly intense interviews. In the first episode, copper Danny was grilled for more than 15 minutes of screen time. The finale features yet another nail-biting interrogation that lasts for nearly half an hour. Bring it on!
Line Of Duty is broadcast on BBC Two at 9pm