**Warning! Major Line Of Duty spoilers below**
Yep, the so-called 'Fourth Man' was unveiled to be none other than the bungling Ian Buckells (Nigel Boyle), who was a key link between the police force and the OCG. Buckells used his links to organised crime to pocket millions, and was secretly living a life of luxury.
But the climax to the BBC's corrupt copper drama wasn't all bad, with Joanne Davidson (Kelly Macdonald) managing to snag the finale's only happy ending.
While the detective had been deliberately misleading the murder inquiry into the death of Gail Vella (Andi Osho), it transpired that she was being pressured by Buckells himself, and had previously been working under Patrick Fairbank as she believed him to be her true father.
After being put behind bars, the OCG attempted to kill Jo by intercepting her police van, after putting in a forged interview request. However, AC-12 had managed to intercept the transfer, and urged Jo to give up the man she was protecting in exchange for witness protection - so she could live the life "she had always wanted", Kate Fleming said.
And in the final few moments of the show, we saw what had happened to Jo after Buckells had been put away.
The once stressed senior police officer now lived in a pretty little cottage with a pet dog and a girlfriend. The caption below reads that Jo now has a new identity and her whereabouts are classified.
Fans may not have liked the way the H storyline transpired, but they were happy to see Jo getting a fresh start in life - and took to Twitter to praise that snippet of the ending.
"At least Jo got to live her Cottagecore lesbian dreams!" wrote one fan.
Referencing a character that had also received witness protection, a second viewer wrote: "Gill Biggeloe must be RAGING at the glamour of Jo Davidson's witness protection."
A third wrote: "I love Line of Duty but that was such a disappointing final episode. My favourite part was Jo's dog at the end..."
"Where is Jo's witness protection cottage and can I rent it on Airbnb?" a fourth queried.
While a fifth said: "Highlights from the Line of Duty final - Jo's dog. That's it."
With over 12 million viewers for the final, this series of Line of Duty has been one of the most popular yet - however, a seventh season is yet to be confirmed.
Writer Jed Mercurio has tweeted a cryptic hint following the finale, which has set fans tongues wagging.
But could this really be the end of a show the nation has become obsessed with?
Line of Duty is available on BBC iPlayer.
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