
Line of Duty — Season 4
If you think catching criminals is tough, try catching police officers.
About this season
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.
Episodes (6)

1. Episode 1
8.2Aired 26 March 2017 • 58 min
DCI Roz Huntley is under intense pressure from her superiors to apprehend a serial murderer after months of fruitless investigation.

2. Episode 2
8.1Aired 2 April 2017 • 60 min
AC-12 crank up their investigation into Operation Trapdoor. Kate makes progress in her undercover role.

3. Episode 3
8.4Aired 9 April 2017 • 60 min
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
8.4Aired 16 April 2017 • 59 min
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
8.2Aired 23 April 2017 • 59 min
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
8.8Aired 30 April 2017 • 58 min
While Nick Huntley faces lengthy questioning, AC-12 remain convinced of Roz's involvement.