Adapted from a famous Wu-Xia series, "The Great Four Detectives", the movie is 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 Heartless, Collin Chou as Metal Hand, Ronald Cheng as Life Chaser and Deng Chao as Cold Blooded, 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 take over the throne.