A young girl is the sole survivor of an attack on her temple. She learns taekwondo from a local merchant. Taking the name 'The Invincible Young-chun', she sets out on a quest for vengence.
The film is set in China, early during its conquest by the Manchu people and their Qing dynasty (1636-1912). The Manchu regime is systematically eliminating Chinese martial art schools and their practitioners, as several of them had joined resistance movements against the conquerors.
The protagonist Yim Wing Chun is the daughter of the master of a martial arts school, which is about to be attacked by a group of Manchu fighters. She asks her father to let her help in the fight, though she is only a novice in the martial arts. He warns her that the Manchu will rape her and does not allow her to stay. During the battle, Yim witnesses the deaths of her father's students and followers. Her father sacrifices his life to allow her to escape. The Manchu warriors initially mistake her for a bystander, but their lieutenant realizes her identity. Meaning that their mission to eliminate this school remains incomplete until she dies.
Afterwards, Yim is wanted by the regime and her face is depicted on printed "wanted" posters. A middle-aged priest helps her during an attack on her person, and nurses her wounds. She learns that the priest is actually a war veteran, whose family and comrades-in-arms were killed in the wars. He talks to her about a Shaolin Monastery which offers protection and Martial arts training to young fighters, and he writes her a recommendation letter.
While departing on ship for the location of the Monastery, Yim witnesses the priest being attacked and killed by a master fighter who serves in the military of the Manchu people. He is an old man, but seems to have superhuman abilities, and to be nearly invulnerable to attacks. Yim is latter accepted in the Monastery. Within the Monastery, the abbot is aware that the new warrior monk, Yim, is actually a nun. But this is kept secret from the other monks, except from one who befriends her and is sworn to secrecy.
After a long period of training, Yim leaves the monastery without permission and tracks down the lieutenant who killed her father. She challenges him to a duel, outfights him, and kills him. But she is then surrounded by his soldiers, and is saved by the timely intervention of the abbot.
Afterwards, Yim receives additional training from an elderly female nun (the abbot's mentor), and is groomed for a mission of assassinating the invulnerable villain. The latter receives a promotion in the imperial ranks, which makes him directly subordinate to the Chancellor of the Manchu court (equivalent to a Prime Minister). The villain gains a right-hand-man in the person of a Japanese master swordsman, send as a tribute to the Manchu court by the government of Japan.
At a later point, Yim, the Abbot, and her best friend lure the villain and his soldiers to a fight away from any human settlements. The soldiers are all easily eliminated, but the main villain confirms his apparent invulnerability by resisting any form of attack, including direct stabbing and slashing with Yin's swords. As they continue to fight, Yim realizes that one part of his body is still vulnerable. She attacks his eyes, blinds him, and causes bleeding in the empty eye-sockets. With the villain dead from excessive bleeding, Yim and her comrades depart from the scene. The film ends.
