余文樂
It is a prequel to the 2002 film "Infernal Affairs". Anthony Wong, Eric Tsang, Edison Chen, Shawn Yue and Chapman To reprise their roles from the original film alongside new cast members Carina Lau, Francis Ng, Hu Jun and Roy Cheung. Neither Andy Lau nor Tony Leung, who played the central roles in the original, appear in this film as they are replaced by their younger versions portrayed by Edison Chen and Shawn Yue respectively. The events of the film take place from 1991 to 1997.