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07/04/2019 10:35 BST | Updated 19/03/2021 16:03 GMT

Line Of Duty Season 3 Recap: Here's What Happened When The Caddy's Story Took Centre Stage

It was the beginning of the end for DI Cottan, as Daniel Mays also joined the cast as Danny Waldron.

While you might have thought we’d seen the last of DI Lindsay Denton after she was sentenced at the end of the second series of Line Of Duty, she made a surprise return as the season three got underway. 

The third instalment of Jed Mercurio’s hit BBC drama also saw Daniel Mays’ character Danny Waldron at the centre of AC-12′s latest investigation, as they discovered how his story intertwined with that of The Caddy and Tommy Hunter. 

As we continue our series-by-series recap, here’s everything that happened...

BBC
Sergeant Danny Waldron was the subject of AC-12's third investigation

Armed response leader Sergeant Danny Waldron was the main suspect of AC-12′s investigation in series three. It kicked off with a raid that ended in Waldron gunning down a suspect, Ronan Murphy, in cold blood, before convincing his team to make it look as if the dead man was shot first.

AC-12 became suspicious about Waldron’s answers when they brought him in to question him, and DS Kate Flemming was subsequently placed undercover  on his team.

Waldron later lurked at the funeral of the man he killed, and followed one of the mourners, Linus Murphy, before breaking into his home and holding him at gunpoint. During the showdown, it was revealed Linus and Ronan had abused Waldron as a child while he was living in a children’s home. Waldron killed Linus and returned to his flat, leaving a list of names, which also included the murdered gangster Tommy Hunter (aka, the one The Caddy had killed in series two), in an envelope addressed to DS Steve Arnott.

Returning to work, Waldron led a drugs raid, during which Flemming was ordered to stay behind as the rest of his team looked upstairs at the property. But after gunshots were fired, Flemming walked into the room to find Waldron had been shot, as the rest of his team stood around him. He later died, and the rest of his team claimed he killed himself.

During an inspection on Waldron’s house, AC-12 connected him to Linus and Ronan Murphy’s murders, while DI Matthew Cottan (aka The Caddy) found the list of names and stole it.

When another of Waldron’s team was found dead in a warehouse, the two remaining officers, PC Hari Bains and PC Jackie Brickford, changed their story and claimed the now deceased PC Rod Kennedy killed Waldron. It was later revealed Bains was a corrupt officer who had killed Waldron under the instruction of The Caddy.

Meanwhile, imprisoned corrupt officer Lindsay Denton had been appealing her case following the events of series two. It was overturned when she revealed she had sex with Arnott while he was undercover, thus exposing AC-12’s failings in their investigation into her.

BBC
Denton began working with Arnott after her release from prison

By this point, AC-12 had connected Waldron and Murphy to Sands View boys’ home, and were on the case of a paedophile ring. Determined to make her way back into the force after her release from prison, Denton agreed to assist Arnott on the case.

Elsewhere, worried about being exposed, Cottan began trying to pin evidence on Arnott that would point to him being The Caddy.

Arnott and Denton then investigated the possibility that Waldron kept a digital copy of his list of abusers, and after tricking Arnott into pursuing a false lead, she sloped off to hack into Waldron’s emails. In his account, she found a photo of the list and sent it to herself, wanting to use it as insurance for her to return to the police force.

However, while at the internet cafe, she was tracked down by Cottan, who summoned her to his car – which actually turned out to be Arnott’s service vehicle but with false number plates. After driving Denton to an industrial estate, Cottan showed his true colours and attempted to blackmail her at gunpoint into sending him the list. After she didn’t agree, he shot her dead, but it turned out she had already sent the list to AC-12.

With the evidence now stacked against him thanks to Cottan’s cunning work, Arnott was arrested for Denton’s murder and on suspicion of being The Caddy.

Flemming then revealed she had actually been undercover investigating her own department under the instruction of AC-3, and had noticed some inconsistencies in Cottan’s line of questioning while interview Arnott, and began to gather evidence against him.

BBC
The Caddy was finally brought down in the series three finale

Eventually, Cottan was brought in for questioning. He initially denied all knowledge when presented with the evidence, but soon unmasked himself as The Caddy. In dramatic scenes, an armed guard in AC-12′s offices turned his gun on members of the team before shooting through a pane of glass in the interview room, allowing Cottan to escape.

Then followed a tense chase scene, where Flemming pursued Cottan, who had escaped in a getaway car. After managing to shoot the driver, she went to confront Cottan, but as passenger in the vehicle fired shots at her, Cottan stepped in to take the bullets.

Fading away, Cottan recorded a dying declaration that lead to the conviction of a police officer – Vice Chief Superintendent Fairbank – who had been involved in the paedophile ring. However, this dying declaration would become even more important in series four, and was revisited in series five...