Line of Duty is back on TV and fans of the show have discovered a striking connection between two characters which may unravel the entire murky plot.
Anti-corruption unit AC-12 is back on the hunt for bent coppers after the stunning expose in series five, which unmasked a number of high-ranking corrupt police officers all said to be working under the guise of shadowy villain H.
Season six featured the return of Detective Superintendent Ian Buckells, played by Nigel Boyle, a character who made his first appearance way back in series one.
He's currently the head of the station and has been making waves, but rewind to the first ever season and he was involved in the investigation into Jackie Laverty's disappearance.
Fans have pointed out he was appointed to the Laverty case by none other than bent copper supremo Superintendent Derek Hilton - which doesn't bode well for him.
However, there's another huge clue which has been spotted by the show's dedicated followers.
Not only was Buckells involved in the first case, he actually interviewed Ryan Pilkington when he was a kid. back in the first series
Ryan was the youngest member of the organised crime gang (OCG) in series five, but his history of the show dates back to series one when he was an active member of the balaclava gang.
His jobs including delivering "burner phones" and making drug deliveries on his bike, even attempting to cut Steve Arnott's fingers off in a particularly grisly scene.
Ryan went on to achieve notoriety in series five when he sit the throat of undercover officer John Corbett, played by Stephen Graham.
At the end of series five, he was seen being accepted into police training and now in this series he's a fully-fledger copper.
Knowing Ryan is quite obviously in the police force for the wrong reasons, fans have put the pieces together and insisted Buckells must be aware of the young copper's real identity - so he must be part of the conspiracy.
DI Kate Fleming, Vicky McClure, seemed to recognise Ryan when she encountered him but couldn't quite place him.
Surely it's only a matter of time before the rest of the squad realise there's a traitor in their midst...
One fan tweeted a screen grab from the first series showing Ryan being interviewed by Buckells and wrote: "Kate can’t place Ryan’s face, but Buckles also interviewed him in Series 1.
"If he’s in his squad now, Buckles for sure knows who Ryan is. Buckles is 100% bent #LineOfDuty."
Another viewer added: "I am 90% certain Ryan said in his interview that he had been in trouble as a kid and it was a police officer that helped him turn his life around and inspired him to apply for the police force so it's not like he has hidden his past ever if Buckells knows...
"And or if / when Kate confronts him about it. The question will surely be can anyone place him as part of the OCG later on. I believe he was kept out of any meetings in S5 where AC12 may have had eyes on but could be wrong."
One more added: "How long til Steve recognises him as the lad that tried to lopping his fingers off with the bolt cutters?"
Another fan also pointed out they'd spotted Buckles had golf clubs and pictures of himself out on the green in his office - another clue which could suggest he's not as he seems.
The link comes from deceased copper and mole Dot Cottan, who earned himself the nickname The Caddy as part of the vast corrupt police officer conspiracy.
Line of Duty returns on Sunday at 9pm on BBC One.
