Infernal Affairs 3 is a Hong Kong film directed by Andrew Lau and Alan Mak, released in 2003. It is the third and final part of the Infernal trilogy Affairs.
Ten months after the murder of Yan (Tony Leung Chiu-wai), Ming (Andy Lau) is relegated to an office job. He is however soon reinstated in Internal Affairs, and wonders about the other moles of Sam, still infiltrated in the police. A member of the Security, Yeung, then appears and seems to have been very close to Sam before his death ... Ming wonders if this man is not one of the last men infiltrated by Sam, who would seek to eliminate him. . Along with this plot, the film takes us back in time, a few months before Yan's death. Yan seems to lose the trust of Sam, who is trying to make a deal with Chinese mobsters. The mysterious Yeung is also present, and Yan wonders about his account. The two cases will eventually come together so that the whole truth finally comes to light.
Andy Lau as Senior Inspector Lau Kin-ming (劉健明), a former triad mole in the police force who tries to cover his past and remain as a cop.
Edison Chen as young Lau Kin-ming
Tony Leung as Chan Wing-yan , an undercover cop. He was killed by Inspector B in the first film.
Shawn Yue as young Chan Wing-yan
Leon Lai as Superintendent Yeung Kam-wing (楊錦榮), Lau's rival in the police force.
Eddie Li as young Yeung Kam-wing
Chen Daoming as "Shadow" Shen Cheng, a Mainland Chinese gang leader who is actually an undercover cop.
Kelly Chen as Lee Sum-yee, Chan's therapist and love interest.
The film's score was composed by Chan Kwong-wing. The theme song, Road to Inferno, was composed by Andy Lau, Chan Tak-kin and Wan Ho-kit, lyrics provided by Andy Lau and performed by Hacken Lee. Lau also sang an alternate version of the song.