After a trio of thieves capture a naïve girl named Gwendoline at a Chinese port, they sell her to a local casino/brothel owner. A mercenary named Willard rescues her before she reunites with her lovely maid, Beth, who the same thieves also kidnapped.
Now free, Willard has to take the two women along with him on a job transporting illegal cargo. You see, Beth is withholding some information vital to his livelihood, and she will only reveal it if he promises to be their guide.
Gwendoline is visiting China in order to capture a rare butterfly that eluded her father. He had staked his entire scientific reputation on obtaining it, and Gwendoline offers Willard $2,000 to take her and Beth with him to the land of the Yik-Yak to find that butterfly.
Along the way, a tribe of cannibal Kiops captures them, but they escape. Soon after, they spot the butterfly. However, as Gwendoline is about to capture it, an all-women tribe’s kidnaps Beth. Now Gwendoline and Willard have to track down their lair to rescue the girl.
This tribe is the last vestige of the city of Pikaho—a diamond mining centre that a volcanic eruption swallowed whole in the 12th century. However, no men remain from it. After the eruption, the entire male population perished from disease, and Pikaho turned into an all-women society of legend.
To ensure Pikaho’s survival, its Queen allows a victor among them to mate with any man who visits the lost city or the tribe captures. Gwendoline disguises herself as a Pikaho warrior with help from Beth and the Queen’s henchman. After much effort, Gwendoline wins the right to bang Willard in honor of the tribe.
As Gwendoline and Willard do the nasty before the Queen, D’Arcy slips away to activate the volcano. Its mighty eruption kills him, the Queen, and the lovely citizens of Pikaho. Gwendoline, Beth, and Willard escape of course. In the end, Willard captures Gwendoline’s elusive butterfly, and isn’t that all that really matters?