Line of Duty

When DS Steve Arnott joins the anti-corruption unit, he learns that the target of his first investigation is the well-respected DCI Tony Gates; though Gates' professional conduct appears above reproach, his private life may provide evidence.

As DS Arnott and DC Fleming close in on his secret, DCI Gates is plunged into an even more dangerous situation.

Arnott is convinced Gates plays 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; her behavior causes Morton to question if she might not be such a loyal colleague after all.

With Gates on the run, the anti-corruption team comes under pressure to close the case; Arnott is forced to make some tough decisions about his loyalties; Fleming and Hastings go all out to catch Gates.