Infernal Affairs

"Internal Affairs" focuses on a police officer named Chan Wing-Yan (Tony Leung), who goes undercover into a triad, and triad member Lau Kin-Ming (Andy Lau), who infiltrates the police department. Each mole was planted by the rival organization to gain an advantage in intelligence over the other side. The more the moles become involved in their undercover lives, the more issues they have to cope with. Lau Kin-Ming wants to be a real cop after being on the verge of being promoted while Chan Wing-Yan feels disillusioned after being a triad member for ten years. Thing take a turn when the triads and cops know that they have a mole within their ranks, each tries to uncover who is their respective mole in their division.