A mad scientist, Dr. Aranya (Jackie Coogan), has created giant spiders in his Mexican lab in Zarpa Mesa to create a race of superwomen by injecting spiders with human pituitary growth hormones. Women develop miraculous regenerative powers, but men mutate into disfigured dwarves. Spiders grow to human size and intelligence.
Jan Horak is a middle-aged railroad dispatcher stationed at a forsaken spot in the desert, within driving distance of the nearest town. A widower, he has saved his money and goes to town to buy a dog, meets Betty, a flashy blonde who gains his confidence and marries him to acquire his $7,000 "fortune."
Tigri and her stone age friends, all of which are women, hate all men. However, she and her Amazon tribe see men as a "necessary evil" and capture them for potential husbands. Engor, who is smarter than the rest of the men, is able to escape them. He discovers fire and battle enormous beasts.
