Detective Chief Inspector Tony Gates is an exemplary cop. He's got the best crime stats on the force and a loyal team working under him. But the head of the police anticorruption unit, Superintendent Ted Hastings, has his doubts about Gates. Is he really that good? And more importantly, is he really that clean? Hastings decides to find out and all on a new arrival to his department, Detective Sergeant Steven Arnott to help him do it. As the net tightens...

Season two has Lindsay Denton, a member of AC12, a police anti-corruption unit, charged with investigating an ambush of a police convoy.

Series follows anti-corruption unit 12 (AC-12) as they investigate fellow police officers accused of corruption. In series five, Stephen Graham stars as John Corbett, the ruthless leader of an organized crime group who hijacks a seized drugs transport. AC-12 investigators suspect corrupt police officers of leaking information. As the body count rises, AC-12 realize they₂re facing their most vicious adversary yet.

A pair of L.A. detectives investigate the death of a teenage girl. Things take a turn for the worse when one of the cops, already under the scrutiny of Internal Affairs, accidentally kills his partner and then covers it up.