Kung Fu's Hero (1973)

Trapped in the world of smuggling young women, our hero, in this 1973 Hong Kong film, is a cop and has fallen for a young maiden. But she is captured by smugglers - who also want to rape the young woman. She also happens to be related to somebody at a kung fu school. The cop goes undercover and joins the gang an then systematically goes about taking the gang apart man by man.