A man trying to run away from a personal tragedy finds out the hard way how much one of his best friends has changed in this action drama. In 2003, Lau Ching-hei (Tony Leung Chiu-wai) and Bong (Takeshi Kaneshiro) are a pair of police detectives who are both partners and close pals. While Bong respects Lau's abilities as a detective, he's wary of his friend's uncertain temper, and he has enough problems of his own to deal with after the suicide of his long-time girlfriend. Three years later, Bong has left the force to become a private investigator and has developed a serious drinking problem, while Lau is one of the top detectives with the Hong Kong police and has married Susan (Xu Jinglei), a respected reporter. Susan and Lau approach Bong and ask him for help with a case -- Susan's father Chow (Yueh Hua) was murdered, and while the team investigating the crime has found two of the men responsible, a third culprit is still at large. Bong agrees to help, but what he and Susan don't know is that Lau is the missing man who helped kill Chow, and he's playing an elaborate game of cat and mouse with his fellow police officers as well as his best friend. Also featuring Shu Qi, Emme Wong and Chapman To, Seung Sing (aka Confession Of Pain) was directed by Andrew Lau and Alan Mak and written by Mak and Felix Chong, the same team responsible for the international hit Infernal Affairs.
~ Mark Deming, All Movie Guide