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The long-awaited Line of Duty series six made its debut on Sunday night, bringing with it a significant character from an early storyline.
Terry Boyle is back at the forefront of a complex murder case - but who is he, whose death was he previously implicated in, and why is his freezer so important?
Here's all you need to know about Terry ahead of the next episode.
Who is Terry Boyle? What's his role in series 6?
Clued up Line of Duty fans will have instantly recognised the name Terry Boyle in series six's opening episode, as he is a minor but significant character whose involvement dates all the way back to series one.
Terry is a man with Down's Syndrome who has been caught up in a number of dodgy situations with the OCG - the organised crime group whose activities relate in some way to every one of AC-12's investigations so far.
He has been used for his flat, his freezer and as a lookout by criminals including Ryan Pilkington (Gregory Piper) in series one and series five, and has now cropped up again in series six, seemingly to take the blame for the murder of journalist Gail Vella.
In the series' first episode, Terry was being questioned in custody after a raid on a flat where he had been left behind by another suspect, Carl Banks, who appears to have been the latest OCG member to use him.
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There was some incriminating evidence against Terry, but not nearly enough to place him as a prime murder suspect, so mysterious DCI Jo Davidson (Kelly Macdonald) decided to let him go.
But with the hunt still on for Carl, no clear proof of who Gail's killer is, and a strangely thorough clean-up having taken place at Terry's real flat (not the place he was arrested) it looks like his part in series six is far from over.
Terry was originally played by Elliott Rosen in series one, but was recast as Tommy Jessop in series five and Jessop has returned for the latest episodes.
When has he appeared in Line of Duty before?
Remember the very first storyline where corrupt DCI Tony Gates (Lennie James) was trying to help his lover Jackie Laverty (Gina McKee) cover up a hit-and-run accident with a dog - actually her accountant, who she'd deliberately killed?
Line of Duty superfans will recall that Terry was used as a pawn by the OCG in series one, as a then-teenage Ryan and his crime pal Carly Kirk (Charlotte Spencer) invited themselves over to his flat and bullied him into using it to hide evidence.
The drama loves a long-running character as both Terry and Ryan, first introduced back in 2012, then cropped up again in series five when an older Ryan began training as a police officer, working as the OCG's inside man in the force.
By this time, Terry was living in a new flat which was handily opposite the printing office serving as a front for the OCG's dealings.
He was supposed to be perfectly placed as a lookout, but we last saw him taking the brunt of Ryan's anger after he missed spotting some investigative activity there.
Meanwhile, poor Terry's freezer was still harbouring some grisly OCG evidence from years earlier, ensuring he stays under the control of the crime bosses...
Why should I care about his freezer?
The contents of Terry's freezer are years old and truly horrifying, with much more than a few out-of-date fish fingers to worry about.
When the OCG murdered Jackie Laverty in series one, they dismembered her body and stored parts of it in Terry's freezer at his original flat.
An understandably panicked Terry tried to alert the police when they searched his flat in series one, but wasn't able to articulate what they should be looking for and so the officers left without realising they had been standing just feet away from frozen body parts.
By series five, we saw that Jackie was still being kept in the freezer, and DCI Davidson and co seemed oblivious to the evidence which had been moved from under their noses at the beginning of series six.
During Terry's questioning about Gail Vella, they referred to a recently removed kitchen appliance and traces of refrigerator chemicals on the floor at his deep-cleaned flat, which viewers will have realised was likely an effort to keep Jackie's body from being discovered.
Could this finally be the series where Jackie is found and laid to rest - and Terry is let off the OCG hook? Somehow, we don't think Terry's untangling from the web of crime will be quite that straightforward.
Watch: Line of Duty series 6 teaser