In the continuing saga of the Corleone crime family, a young Vito Corleone grows up in Sicily and in 1910s New York. In the 1950s, Michael Corleone attempts to expand the family business into Las Vegas, Hollywood and Cuba.

Chan Wing Yan, a young police officer, has been sent undercover as a mole in the local mafia. Lau Kin Ming, a young mafia member, infiltrates the police force. Years later, their older counterparts, Chen Wing Yan and Inspector Lau Kin Ming, respectively, race against time to expose the mole within their midst.