An interesting take on hypnosis, Heroic Duo tells the story of a detective named Ken (Ekin Cheng) who is investigating an officer who set fire to the police station vault. Ken, believing the officer had been hypnotized, brings in a psychologist turned convict Jack (Leon Lai) to assist in finding out who hypnotized the officer. During their first meeting Ken becomes hypnotized by Jack who then escapes, and a game of cat and mouse ensues.