Tarzan is baffled when an injured man rides into a Zambesi village and, before dying, reports that the caravan he was traveling with was destroyed by leopards.  Knowing that leopards kill with their teeth as well as their claws, Tarzan tells the commissioner of Zambesi that the man, who only has scratch wounds, could not have been attacked by leopards.  The commissioner dismisses Tarzan's verdict and forms a safari to hunt the killer leopards.

Before the safari leaves for the jungle, the half-white Dr. Emir Lazar, who seemingly embraces the white man's culture, informs his secretive, cave-dwelling tribe about Tarzan's suspicions.  Lazar and Lea, the tribe's high priestess, decide that in order to protect their homeland of Bagandi, which is being invaded by Westernized Zambesis, they must ridicule Tarzan and continue their attacks on Zambesi caravans.  To that end, they order real leopards to attack the safari, which has been joined by Tarzan, his wife Jane, their son Boy and their pet chimpanzee Cheetah.  Although Tarzan kills several leopards himself, he still doubts that they were responsible for the caravan deaths and is mocked by the commissioner.

Unknown to Tarzan and the safari, the hunt is being watched by Lea's young brother Kimba.  The petulant Kimba, who is disliked and mistrusted by Lazar, decides that he will earn his manhood by killing Tarzan and his family.  Pretending to be lost and hungry, Kimba appears at Tarzan and Jane's jungle home and asks for refuge.  Although Tarzan and Boy are suspicious of Kimba, Jane insists that they care for him until his tribe is located.  While Tarzan and Boy are collecting bamboo for their outdoor shower, Kimba steals a knife from Jane and dresses up in his tribe's leopard skin attire.  Tarzan and Boy return home just as Kimba is about to lunge at the unsuspecting Jane.

Later, as the commissioner reassures a group of young Bagandi-bound Zambesi teachers that their caravan will be safe, Lea and Lazar rally their warriors to ambush the teachers.  Then, while the young Zambesis are set upon by the warriors, Boy is nearly mistaken for Kimba when he unwittingly dons his leopard skin.  Alerted by Cheetah, Tarzan rescues Boy from the Bagandis' clutches and almost saves the teachers, but is caught.  Kimba then tries to kill Jane and Boy, but is knocked out by the ever-resourceful Cheetah and is locked in a bamboo cage by Boy.

In the Bagandis' cave, meanwhile, Lea demands that Tarzan, who is tied to a pole, tell him where Kimba is, then orders her men to kidnap Tarzan's family.  After a fierce fight, Boy and Jane are overwhelmed by the Bagandis and brought to their cave.  There, Lea and Lazar order that all of the teachers and Tarzan and his family be sacrificed to their leopard god.  As the warriors are performing their sacrificial dance, however, Cheetah sneaks in and unties Tarzan, then frees Boy and Jane.  When Tarzan brings down the pole to which he is tied, he causes the ceiling to collapse and precipitates a cave-in.  Moments before the cave's total destruction, Tarzan witnesses Kimba shoot Lazar and then be crushed by the falling rocks.

Their ordeal over, Tarzan, Jane, Boy and Cheetah happily return to their jungle home.