Kline (Josh Hartnett) is ex-Los Angeles cop, who is haunted by the memories of the serial killer Hasford (Elias Koteas) who almost made him insane and made him quit the LAPD. Now a private detective, Kline is hired by a powerful Chinese billionaire to find his missing son, Shitao (Kimura Takuya). He travels to Hong Kong and enlists the help of an old friend, Joe Men Zi (Shawn Yue) who works for the Hong Kong Police. Following Shitao’s traces leads him to Su Dongpo (Lee Byung-hun), the local gangster and his drug addicted girlfriend Lili (Tran Nu Yen Khe). However Hasford’s memories keep coming back and distract him from his search.