Watch FMovies. Lau Leung-wah plays the titled character, a Chinese Robin Hood who robs the rich to help the poor. She is an early Republican Era Mulan, who switches effortlessly between charming gentility and agile ferocity, and Lau personifies her character's duality with a balance of grace and vigour. Chang Cheh, on the verge of fostering seismic changes in cinema with his martial-arts machismo, pens a script that captures the spirit of changing Chinese womanhood, underscored by a conflict between Black Butterfly and her father, a veteran detective.