Please answer the following question: Build a movie plot around this: What is Lau Kin-ming Sam's secret activity? Rookie police officer
A:
Act 1The film opens eleven years prior to Infernal Affairs in 1991. Inspector Wong Chi-Shing (Anthony Wong reprising his role) is discussing the death of his first partner with an initially unseen companion, who is revealed to be Hon Sam (Eric Tsang, also reprising), the triad boss from Infernal Affairs. At this point in time Sam is a follower in Ngai Kwun's triad family and is also working as Wong's informant. Carrying a nondescript paper bag, a young Lau Kin-Ming (Edison Chen) makes his way through the streets of Mongkok. Ming stops at an ostensible martial arts school where Ngai Kwun is spending the evening. With a gun concealed in his paper bag, Ming kills Kwun and walks away.Ming arrives at a secluded office space where Sams wife, Mary (Carina Lau), greets him. Mary is testing her new stereo system, playing the exact same song Ming used to test his system in Infernal Affairs; she sardonically praises it to Ming in the exact manner that Yan does in the first film while casually ascertaining whether or not he has any reservations about being Sams mole in the police force. Appearing aloof, Ming accepts the position and Mary packs a bag of cash for him, advising that he maintain a low profile and prepare for the police academy; assuming that the song she put on the stereo is distracting him, she also gives him a copy of it. Ming is attracted to Mary, but is unwilling to express it due to his lowly position in the gang. It is then revealed that Mary ordered Kwuns assassination. Mary confesses that Sam has no knowledge of this transgression and urges Ming to keep it that way, as she wants Sam to take Kwun's place as leader of Ngai family triad.Meanwhile, we see a young Chan Wing-Yan (Shawn Yue), his girlfriend and a young Crazy Keung (Chapman To) are waiting for something. Yan is a promising police cadet who has apparently assaulted and subdued Keung over a car theft. Superintendent Luk Kai-Cheung (Hu Jun) arrives on the scene with several officers. Luk admonishes Yan about his actions but decides not to...