Line of Duty - Season 4

First aired: 3/25/2017 6 episodes

The fourth series sees AC-12 facing their most devious opponent yet! Under pressure from her superiors, DCI Roz Huntley charges a young man with a series of murders after months of fruitless investigation, but is he guilty? The Chief Forensic Investigator has doubts and turns to AC-12.

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Episodes

1. Episode 1

Aired: 3/26/2017

DCI Roz Huntley is under intense pressure from her superiors to apprehend a serial murderer after months of fruitless investigation.

2. Episode 2

Aired: 4/2/2017

AC-12 crank up their investigation into Operation Trapdoor. Kate makes progress in her undercover role.

3. Episode 3

Aired: 4/9/2017

As AC-12 wrestle with the new forensic evidence casting doubt over Tim Ifield, Kate is approached by another woman claiming to have been assaulted by Michael Farmer.

4. Episode 4

Aired: 4/16/2017

Roz's husband Nick is brought in for questioning by AC-12. But while Nick denies any involvement in Steve's attack, his suspicions about Roz mount.

5. Episode 5

Aired: 4/23/2017

DCI Roz Huntley struggles to allay her husband's suspicions. AC-12 find a new angle to pursue their case against her.

6. Episode 6

Aired: 4/30/2017

While Nick Huntley faces lengthy questioning, AC-12 remain convinced of Roz's involvement.