Chan, an articulate senior detective nearing the end of his career, is taking care of the daughter of a witness killed by ruthless crime lord Po. Martial arts expert Ma is set to take over as head of the crime unit, replacing Chan who wants an early retirement.

So goes to the U.S. to open a martial arts school. Around this time, many Chinese people were sold off to U.S. railroad companies, and were brutally treated by the Americans under the harsh working conditions. Thus, the American workers' hatred towards the Chinese immigrants is high. As a result, So gets into trouble with the Americans and the mob, and calls Master Wong for help.