A scientist develops a formula which will cause animals to regress to the form of their primitive ancestors, and tries it on himself with disastrous results.

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.

A medical student learns about a scheme to drug a girl and pass her off as an heiress to an oil fortune.