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