S Steve Arnott is transferred to the police anti-corruption unit after the death of a man in a mistaken shooting during a counter-terrorist operation by another cop.
Martin Compston Steve Arnott
Vicky McClure Kate Fleming
Lennie James Tony Gates
Adrian Dunbar Ted Hastings
Neil Morrissey Nigel Morton
Craig Parkinson Matthew 'Dot' Cottan
Steve Arnott realises the target in his anti-corruption case is the city's top detective.
Having been duped into covering up Jackie's crime, Gates tries to sever ties with her.
Arnott is convinced Gates played a part in Jackie's disappearance.
Desperate for proof of Gates's corruption, Fleming pushes their relationship to the limit.
With Gates on the run, the anti-corruption team come under pressure to close the case.