Line of Duty

When Steve Arnott is transferred to AC-12, his first assignment is to investigate the city's top detective, DCI Tony Gates.

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

Desperate for proof of Gates's corruption, Fleming pushes her relationship with him to the limit.

With Gates on the run, AC-12 comes under pressure to close the case once and for all.