Episode 5 of Line of Duty airs Tuesday 24 July at 9pm on BBC Two.
With Gates on the run the anticorruption team come under pressure to close the case.
Tensions flare between Arnott, Fleming and Hastings, as Arnott questions how intimate Fleming was prepared to get with Gates.
Meanwhile, Gates still believes he can save his career and marriage, if only he can prove his innocence. Arnott is forced to decide where his loyalties lie, while Fleming and Hastings go all out to catch Gates – leading to a shattering conclusion.
DCI Tony Gates is played by Lennie James, DS Steve Arnott by Martin Compston, DC Kate Fleming by Vicky McClure, and Superintendent Ted Hastings by Adrian Dunbar.
© BBC/World Productions/Ed Miller