Infernal Affairs III is a 2003 Hong Kong crime action film directed by Andrew Lau and Alan Mak.

Infernal Affairs III received mixed to positive reviews, grossed $4.5 million and was nominated for seven Hong Kong Film Awards.

His superior, Superintendent Wong Chi-shing, persuades the court to allow Chan to seek therapy, leading him to meet therapist Lee Sum-Yee.

After months of investigation, Lau is reinstated back to Internal Affairs, where he struggles to conceal his criminal past and protect his true identity.

Lau later learns that Hon had previously planted five other spies in the police force, one of whom might be a fellow Security Division Inspector, Yeung.

Meanwhile, Lau suffers from an identity collapse as he loses track of reality, wrestling with guilt over Chan's death and grappling with his impending divorce from his wife, Mary.

After witnessing an incident where Lau suffers a hallucination, Lee conducts a hypnosis on him and finds out that he was Hon's spy.

Lau ends up crippled and catatonic, lost inside his own mind, haunted by the spirit of Mary (Hon Sam's wife, whom he had a crush on in Infernal Affairs II) and locked in his own "continuous hell".

Before the film ends, there is one final flashback to the hi-fi shop scene in Infernal Affairs, where Lau is buying an audio system from Chan.

"[4] Derek Elley from Variety noted its use of "copious flashbacks" and its rushed ending, writing that "there’s a growing sense of the writers thrashing around to provide a finale.

"[5] Manfred Selzer from AsianMovieWeb gave the film a rating of 7 out of 8, praising it for delivering "a big deal of thrill, tension and has a great story to hold everything together, which makes the third part, too, a movie experience," although he felt that "the finale feels a bit like a neverending epilogue, which didn't know where to find an end.

"[6] Ross Chen from LoveHKFilm wrote that "Infernal Affairs III is not tightly crafted like the first film, nor meaty and dramatic like the second."