This second part of the Infernal Affairs trilogy is set ten years prior to the showdown witnessed in the first film. Here we find Yan and Ming at the very beginning of their careers, one a young police officer undercover with the triads, the other a triad infiltrating the cops. Infernal Affairs II is every bit as slick as the first, an intelligent action thriller that fleshes out the central characters' motivations and, in a pleasantly frustrating way, makes a second watching of Part One unavoidable.