Meet Dr. Bernard Adrian (Boris Karloff), a kind, friendly, caring scientist who has made it his personal mission to cure a young woman’s polio. From his research he determines that all he needs is spinal fluid from a human to complete the formula for his experimental serum and if that works he will have invented a cure for polio.
Meanwhile, a vicious circus ape named Nabu (Ray “Crash” Corrigan) has broken out of its cage and has become a physical threat in the town.
Nabu the Ape makes his way to Dr. Adrian’s lab and smashes his way inside. Luckily Dr. Adrian manages to kill it before any harm can come to himself. However, the spinal fluids he requires to perform his experiments have all been destroyed during the struggle between him and the Ape.
Luckily Doctor Adrian has a cunning plan! He decides he will tear off the ape’s flesh and use its skin to disguise himself as the escaped ape and murder townspeople in order to extract their spinal fluid. The murders will of course be blamed on the Ape and Dr. Adrian will be free to continue his research.
How can a plan like that go wrong?