The movie is adapted from a famous wu-xia series, The Great Four Detectives, written by Wen Ruian (温瑞安). There is also a popular TVB drama based on the story. Director, Chan, told the Chinese media that his interpretation of the story will bring a fresh spin to the tale of four detectives skilled in martial arts that are hired by the Emperor to solve various mysteries. The four detectives, Liu Yifei as Emotionless 无情， Collin Chou as Iron Hands 铁手，Ronald Cheng as Life Snatcher 追命and Deng Chao as ColdBlood 冷血, have individual special powers. They are strict and impartial, seeking justice on behalf of the citizens and even discovered the secret plot of evil minister planning to usurp the throne! The huge responsibility of the country now falls on The Four.