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. Meanwhile, AC-12 discover new anomalies in the forensic evidence and issue DCI Roz Huntley with a second Reg 15 notice. AC-12's case appears watertight until Roz starts dismantling their evidence with inside information of her own.

Line of Duty Season 4 Episodes...

• s04e01 - Series 4, Episode 1
• s04e02 - Series 4, Episode 2
• s04e03 - Series 4, Episode 3
• s04e04 - Series 4, Episode 4
• s04e05 - Series 4, Episode 5
• s04e06 - Series 4, Episode 6

Line of Duty Show Summary

Steve Arnott is a young officer who's fallen foul of his superiors for refusing to help in the cover-up of an operation that ended in the shooting of an innocent father. He seems ideal to join AC-12, an anti-corruption police unit, just as it starts to investigate Detective Chief Inspector Tony Gates, the regional force's Officer of the Year.