Infernal Affairs III splits itself into two intercut strands:
This structure intentionally blurs chronology and perspective—scenes overlap with earlier films, and new footage recontextualizes past actions. The result is less a linear narrative than a palimpsest: the past never fully lets go.
The film was a commercial success, grossing over HK$47 million (US$6 million) at the Hong Kong box office.
Infernal Affairs III was initially criticized as convoluted. But over time, it has been reassessed as a brave, experimental conclusion. It is not an action film; it is a psychological horror movie disguised as a police thriller.
Watch it for:
Yeung Kwun (Leon Lai) is the film’s red herring. He appears cold, calculating, and suspicious. But his role is tragic: he is another undercover cop, inserted into the Police Complaints Division to root out corrupt officers. He is not hunting Lau for being a mole; he is hunting Lau for the murder of SP Wong (from the first film).
By the end, Yeung Kwun is killed by Lau, making him yet another innocent cop sacrificed to protect a lie.
Leon Lai’s Inspector Yeung is the film’s most controversial addition. On the surface, he appears to be a deus ex machina—a new character who shows up with a cryptic smile and throws a wrench into both timelines.
But Yeung is not a character. He is a mirror.
In the past, Yeung investigates Chan Wing-Yan. He doesn’t trust the young, reckless undercover cop. He pushes him, tests him, almost breaks him. But in doing so, he inadvertently solidifies Chan’s resolve. Yeung is the impossible standard: a cop who is truly incorruptible, utterly silent, and lethally effective.
In the present, Yeung becomes Ming’s persecutor. He sees through Ming’s facade. He doesn’t have evidence, but he has instinct. Every time Yeung appears, Ming’s composure cracks. Yeung is the guilt Ming cannot articulate, the internal affairs officer of his own conscience.
The film’s final twist—revealing Yeung’s true allegiance and his tragic fate—recontextualizes the entire trilogy. It suggests that there was always a third player, a silent guardian watching from the shadows. Yeung’s death is not heroic in the conventional sense. It is quiet, bureaucratic, and heartbreaking. He is a good man who loses because the system doesn’t reward goodness; it rewards survival. Ming survives. Yeung does not. That is the horror.