When a counterterrorism raid goes tragically wrong, Detective Sergeant Steve Arnott refuses to participate in a cover-up. Ostracised by colleagues, he transfers to an anticorruption unit, AC-12, in the process of investigating one of the Force's most respected officers, Detective Chief Inspector Tony Gates. Not only has Gates just been awarded Officer of the Year, his squad has returned the best crime figures for three consecutive years. But can anyone really be that good? Arnott doesn't think so and soon he and Gates are embroiled in a game of cat-and-mouse but as the stakes get higher it isn't just careers on the line it's lives.