Somewhere in the early Ming Dynasty, the Pope of Happy Religion is a lustful monster, who can assume male or female form at will (the female form is Pauline Chan in a white wig). His/her forces fly around and attack Dr Yue and his family, including his daughter Bao, who has her back invisibly tattooed. The village chief (Ho Ka Kui, under a heavy beard) bravely fights to the death.
Sixteen years pass. Chao Chuen is a poor scholar carrying his overweight mother around in a backpack.
(Where he finds the strength to do this is never explained). Mum has an eye disease, and Chuen is seeking a legendary doctor to find the cure.
Chuen encounters the Pope's chief assistant, who is playing a zither, and tries to distract him, but is thwarted by two tramps to whom he previously gave water.
As a man, the Pope practices what he preaches, and has a cackling great time. He practices the Evil Laugh most often whilst deflowering the local virgins, from whom he draws lifeforce. But one of the girls he beds gives him a headache because, it turns out, she's not a virgin.
Instead of aspirin, he urgently needs another virgin to restore chi (or, at least, that's his excuse !).
Unfortunately, there are none left, apart from his two pretty acolytes Wan and the now-adult Bao. With some persuasion, they submit to their master.
Bao has already crossed paths with Chuen, and asks for his protection (which, of course, leads to a couple more sex scenes). They find Dr
Yue again, who has scripts of the cure which, because they are written in "Fan", he can't read. But Chuen can.
After Bao sleeps with Chuen again, her invisble back tattoos appear again, and they also are in written in Fan. Translated, they help Dr Yue cure Mum's eye problem and show that Bao was given the power (in childhood) to defeat the Pope. Lots of explosions, swordplay, flying around and blood-letting later, good eventually triumphs over evil, and Bao's tattoos vanish again.