Where's Officer Tuba?

Officer Tuba (Sammo Hung) and Police Detective Chow (David Chiang) attempt to hunt down a band of blackmailers. Unsuccessful in capturing the gang, Chow is gunned down and, in his dying moment, makes Tuba promise that he will defeat the gangsters and avenge his death. When Tuba goes on another police mission with rookie Cheung (Jackie Cheung) and tries to woo his girlfriend-to-be Joanne (Joey Wang), he forgets his promise to Chow. Therefore, Chow's spirit appears and haunts Tuba, attempting to make him fulfill his mission.