10 months after the murder of Chen Wing Yan (Leung), the investigation is closed with the conclusion that Ming (Lau) successfully took out the Triad's mole. Relegated to a benign office job and his marriage over, a new star enters the IA team, in the form of the up-and-coming Superintendent Yeung, whose meteoric rise mirrors that of Ming. Suspecting that Yeung is a mole like he was, Ming begins to investigate the new hot-shot...

Involving a complex flashback narrative binding the new investigation with the previous events from the first film, Infernal Affairs 3 has invited favourable comparisons with Francis Ford Coppola's classic Godfather trilogy.