In the prequel of Infernal Affairs. Chan Wing Yan has been expelled from police academy in cause of his relatives to the triad. Now SP Wong give him a chance to undercover the triad family controlled by his half brother Hau. Besides of Ming. He has been ordered to killed Hau father and infiltrated the police department. The story get complicated when Wong's related to Hau father's dead. The avenge is begin when Mary. Sam's wife is the hit order. Now everything is complicated and related Written by PDD

Wong Kam-Kwei, a gang boss on the decline, overseeing bathhouses and karaoke bars, falls for a small restaurant owner, Mei. He begins to help her business, and learns that Mei is already in love with Leung, a member of his gang. He’s also like a brother to Kam-Kwei. When a rival gang hoping to steal his territory kills Leung, the only thing left for Kam-Kwei to do now is to protect Mei and avenge Leung.