Bong (Kaneshiro) quits the force after a traumatic loss, the ramifications of which are revealed only towards the end of the film. Once teetotal, Bong becomes a heavy drinker. Hei (Leung), who has recently married, remains close to Bong, who now works as a private detective.
When Hei's father-in-law is murdered, Bong is retained to investigate alongside the police: when the killers are tracked down, he continues, with Hei's encouragement, to follow the case.
