The plot follows the titular sisters, Ruo Lien, Ruo Lan and Ruo Mei whose clan protects the famous mighty steel sword, a powerful weapon much sought after by their rivals, in particular the nasty Chu Tien Hsiang (played by the legendary actor Lo Lieh, known at the time for being the studio's first international superstar, appearing in the likes of "King Boxer" and "Lady Hermit") who aims to use it to become number one in the martial arts world. Infiltrating the trio with his cunning schemes, he seizes the blade and sets about eliminating its rightful owners as the girls band together to bring him to justice.