Professor Kiu is a mad scientist who developed mental disorders from grieving the death of his son. Kiu orders his assistants to kidnap men to his lab, located in a private container on a vessel, for experiments. Police inspector Uncle Wah had sent his subordinates to gather evidence in the vessel, but failed to find any. Shek La-mai, an acrobatic performer and a former commander of the Special Duties Unit is a single father of three children. One night during a performance with his protege, Lam Hong, witnessed and intervened in a kidnapping incident by Kiu's henchmen, and the two became targets of Kiu. On the other hand, Uncle Wah discovers Shek's resemblance to a Japanese scientist named Toyota, who colluded with Kiu. Wah formulates a plan for Shek to act undercover as Toyota in order to gather evidence from Kiu's lab.
