DS Steve Arnott believes there is a dark secret in Danny Waldron's past. But while DI Cottan is commended for cracking the Waldron case, the spotlight falls on Arnott's questionable conduct in a previous enquiry.

Line of Duty Season 3 Episodes...

• s03e01 - Series 3, Episode 1
• s03e02 - Series 3, Episode 2
• s03e03 - Series 3, Episode 3
• s03e04 - Series 3, Episode 4
• s03e05 - Series 3, Episode 5
• s03e06 - Series 3, 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.