Line of Duty series 1-3 recap: everything you need to know before the BBC drama returns

Get up to speed on the first three series of the BBC's thrilling cop series ahead of the new episodes

What happened in Line of Duty series three?

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Armed response team leader Sergeant Danny Waldron (Daniel Mays) became the subject of AC-12’s investigations after a suspect was shot dead in suspicious circumstances.

However, in a shocking twist, by the end of the episode Waldron himself was dead, apparently killed by one of his own team. What was going on?

It transpired that Waldron had a list of names of people who had sexually abused him and his schoolmates as a child, and was taking revenge. The paedophile ring included high-profile politicians, policemen and celebrities – including, in a disturbing nod to real events, Jimmy Savile.

Waldron had tried to leave a copy of the list for DS Arnott, but dodgy Dot – now in charge of the investigation – discovered the record of names and destroyed it.

So, was that where the evidence trail went cold? Not quite.

In a surprise return that caught everyone off guard, DI Denton’s conviction was overturned on appeal, and the series two anti-heroine was free again. Despite her trial revealing key failings in AC-12, in the end she agreed to assist Arnott in cracking open the child abuse case by discovering a back-up version of the list (remember, it was witnessing abuse in series two that dragged her into the ill-fated police convoy).

It was Denton, too, who finally discovered Dot’s true identity as the corrupt mastermind turning everyone’s heads in the wrong direction. In a grim showdown, Dot shot Denton through the head – but not before she managed to deliver a digital copy of Waldron’s list of abusers to AC-12.

While Dot had attempted to frame Arnott as the corrupt insider, Fleming wasn’t buying it. In a feature-length finale, Dot was finally unmasked as ‘The Caddy’ in a riveting interview scene.

Dot had planned his escape route long ago, however, and in a spray of bullets and shattering glass escaped the interrogation room, only to have Fleming chase him down.

The ensuing chase saw Dot jump in front of bullets from a mystery assailant to save Fleming’s life, recording his ‘Dying Declaration’ for his colleague before passing away – evidence that would help bring the abusers to justice.

So, Dot is dead, and Fleming and Arnott are reunited with boss Ted Hastings. A fresh start for series four? Perhaps – although, if the first three series have taught us anything, it’s that the web of corruption stretches far and wide. The Caddy isn’t the only bad apple…

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This article was originally published in March 2017