DS 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.
When a counterterrorism raid goes tragically wrong, DS Steve Arnott refuses to participate in a cover-up. Ostracised by colleagues, he transfers to an anti-corruption unit led by Supt. Ted Hastings. He soon finds his target is the city's top detective, DCI Tony Gates. with whom he must engage in a cat-and-mouse struggle to uncover Gates' secret.
Having been duped into covering up Jackie's crime, Gates is desperate to sever ties with her. But, as Arnott and Fleming close in on his secret, Gates is plunged into an even more dangerous situation than he first thought.
Arnott is convinced Gates played a part in Jackie's disappearance. With Fleming's help, the anti-corruption team tries to trap Gates into revealing his involvement in covering up Jackie's crimes.
Desperate for proof of Gates's corruption, Fleming pushes her relationship with him to the limit, but her behaviour causes Morton to question her loyalty.
Gates goes on the run, convinced he can save his career and marriage by proving his innocence. As his options dwindle, the anti-corruption team faces renewed pressure to close the case, but rifts start to appear when Arnott questions how far Fleming is willing to go to get results.