Devoted Line of Duty fans who've watched from the start may remember a central character in previous seasons - the 'Caddie'.
Played by Craig Parkinson, DS Matthew 'Dot' Cottan was known to be an inside man in the BBC series.
Dot entered the world of crime at a young age when he was working as a golf caddie for gangster Tommy Hunter, who groomed him into a life of crime.
He then went on to work his way into AC-12 and continue his criminal work from the inside under the nickname the Caddie.
However he was killed in a later season but not before revealing he was promoted by another corrupt policeman, nicknamed H.
Now clues in recent episodes are leading fans to think the Caddie has returned.
Hints such as strategically placed golf clubs and golf pictures on his office walls are leading viewers to think that detective superintendent Ian Buckells may have links to the Caddie or the crime world.
@DanLikesMerch tweeted: "They love sticking Buckles around golf clubs don’t they #Caddy #LineOfDuty."
@Owen_Ibberson added: "Buckells is playing around with golf clubs could thus be referring to Matthew cottons suggestion of someone relating to a Caddy."
@racheyrooney said: "Anyone else shout Caddy! When they saw Buckells with the golf clubs?! #LineOfDuty. "
While @ItsSophieAnna commented: "Buckells in his office with golf clubs and golf photos up on his walls and then being called ‘The Hill’ H? The real caddy? Hmmm #LineOfDuty."
@hearmeplaypiano said: "Okay, those golf clubs last week were a subtle nod, but that wasn’t. Definitely caddy connections. Buckles, you bent b******!"
Line of Duty returns to BBC1 on Sunday evening at 9pm, or previous episodes can be found on the BBC iPlayer.
