In Brazil, Dr. Ann Philips tries to inoculate the superstitious natives against an epidemic. The murderous Jaguar Men oppose the intrusion. The natives take heart when the riverboat captain's helper Pepe volunteers for the first shot.

Tarzan travels to South America at the request of his old friend, a Professor who believes an ancient cult is preying on the local native population. He soon dons his loincloth and with Cheetah and pet lion Baron travels up the Amazon river. He meets up with Captain Sam Bishop and his young ward Pepe and all of them are soon in the hunt for the Jaguar Men and their leader Barcuna. Tarzan rescues a pretty doctor, Ann Phillips, after her jungle hospital is burned to the ground. Together, they set off into the jungle to confront the cultists who are enslaving the local population.—garykmcd

At the request of his old friend, Tarzan travels to South America to prevent the charismatic but evil tribal leader, Barcuna, and his murderous Jaguar Cult from pillaging native Amazon River villages and enslaving the survivors. After the death of a dear one, mighty Tarzan swears revenge and takes Cheetah, the chimpanzee, and Baron, the lion, into the peril-laden jungle. There, against the backdrop of an epidemic, Tarzan meets three unexpected allies: the tough riverboat pilot, Captain Sam Bishop, his young ward, Pepe, and the idealist American physician, Dr Ann Philips. Can Tarzan save the Great River and put an end to Barcuna's relentless reign of terror?—Nick Riganas