The film features all the members of the popular Hong Kong 'Cantopop' group EO2, playing Triad boss Hom Sam's men. One member of this group has subsequently become a lead actor (Osman Hung). Miramax Films acquired the United States distribution rights of this film and gave it a limited US theatrical release in 2004.
Plot (Spoilers Ahead): Infernal Affairs focuses on a police officer named Chen Wing-Yan (Tony Leung Chiu-Wai), who goes deep undercover into the Triad society, and Triad member Lau Kin-Ming (Andy Lau Tak-Wah), 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.The Prologue opens with the introduction of Hon Sam (Eric Tsang Chi-Wai), a Triad boss and the primary antagonist of the film. Sam is sending a number of young, green gangsters to the police academy as molesamongst them is one called Lau Kin-Ming (whose younger version is portrayed by Edison Chen Koon-Hei). At the same time another person named Chen Wing-Yan (whose younger version is portrayed by Shawn Yue Man-Lok) is shown joining the police force. Although he manages to impress the Superintendent Wong Chi-Shing (Anthony Wong Chau-Sang) and the police academy principal Yip, Yan is expelled from the academy. In reality Yan becomes an undercover reporting directly to only Wong and Yip. Yan's undercover job becomes stressful while Ming quickly climbs the ladder in the police department.
Later, Sam converses with Ming at a cinema with Yan watching. As Sam and Ming leave, Yan tries to follow Ming. At the crucial moment, Yan's phone rings and he is forced to back off, thus losing his chance to capture Ming.
At the same time, Yan and Ming are both struggling with their double identities. Yan is starting to lose faith in himself as a cop after being a gangster for ten years; while Ming, on the other hand, becomes more and more used to the life of a righteous police officer and wants to erase his criminal background.
Yan meets SP Wong a second time on the same rooftop unaware that Ming has his subordinate, CIB Inspector B (Gordon Lam Ka-Tung) and his team tracking him down. Sam, after getting intel from Ming, sends Keung, Del Piero and a gang of henchmen to confront them. Inspector B informs Ming and he sends an OCTB squad to attempt to save Wong. Yan eventually escapes the building by taking the crane but Wong is caught by Del Piero and is thrown off the roof. As Yan is about to escape, he witnesses Wong's fall to death, and is stunned. As the police close in, a shootout between the police and Triads breaks out, resulting in the death of 3 Triads, one of whom is Del Piero. In the aftermath of the gunfight, the OCTB squad arrives with Ming and Wong's second-in-command Inspector Cheung (Berg Ng Ting-Yip) on the scene, but they are too late to save Wong. Yan and Keung manage to escape from the gunfight. As Keung drives away with Yan, he crashes the car, and finding that he is wounded from the gun battle, Keung dies in Yan's arms.
Eventually, Ming retrieves Wong's old cellphone and makes contact with Yan. They reach a deal to foil another one of Sam's drug deals. Inspector Cheung does not want to cooperate with the operation at first because of Wong's death, but he is later convinced by Ming to go ahead with the operation. With Yan's help, Sam's drug deal is interrupted and Sam is killed by Ming. Many of Sam's other gangsters are arrested. Everything seems to work according to the plan: Yan could now return to his true identity as a police officer and Ming has successfully erased his criminal connections by eradicating Sam and his gangs. However, back at the police station, Yan discovers Ming was the mole, and leaves immediately. Ming realizes what has happened, and erases Yan's identity from the police computer records. Yan spends an evening with his therapist Lee (Kelly Chen), whom he was falling in love with, and sends a compact disc to Ming which is inadvertently intercepted by his wife Mary (Sammi Cheng Sau-Man) with a recording that Sam kept between himself and Ming. The two agree to meet on the rooftop of the building where Wong was murdered earlier. Yan disarms Ming without resistance. Yan holds a gun to Ming's head as rebuke and as reply to Ming's plea for forgiveness to remain a policeman. Inspector B arrives on the scene shortly afterwards and commands Yan to release his boss.
The film ends with Yan entering a lift backwards with Ming hostage, when he is suddenly shot in the head and killed by Inspector B as he moved his head from behind Ming. Inspector B reveals that he was also a mole for Sam. He asks Ming to watch out for him, since their boss is already dead. As he and Ming enter the lift going down to the lobby, Ming shoots Inspector B dead, likely out of his desire to eradicate traces of his past and become a "good guy" police officer.The original ending climaxes with Ming identifying himself to the police as an officer, and paying homage to Yan at his funeral, where he is buried next to Superintendent Wong. Inspector Cheung and Dr Lee are present as well. A flashback reaffirms the point that Ming wished he had taken a different route in his life.
Alternate Ending
The alternate ending has Ming exit the lift to be informed by Inspector Cheung that the police force have found evidence that he was a mole. He hands them his badge and is arrested without protest.
The quality of film was duly recognized at the 22nd Hong Kong Film Awards in 2002, where it won all the major awards (best film, best director, best screenplay, best actor). It's high quality Hong Kong Cinema and ranks among classics such as The Killer, Hard Boiled, and Crouching Tiger Hidden Dragon. If you loved The Departed then this film and it's two sequels are worth seeking out and we highly recommend it!
