Upon saving a woman named Thia from the Bulgani gorilla tribe, Tarzan learns that she is from Athne the City of Ivory and had been chased away by enemy soldiers from Zandor the City of Gold. While helping Thia back to Athne, Tarzan ends up captured by the Zandorians. While imprisoned, Tarzan meets his cellmate Phobeg who tells him of Queen Nemone who has the two of them fight in the arena. Once Fobeg is freed, Tarzan ends up incarcerated with Thia after harming her prime minister Tomos. However, Fobeg has a plan to free Tarzan and Thia.
A race of jungle vikings (who are descendants of the vikings that were blown to Africa by a north wind sent by Odin 1,000 years ago) capture Tarzan to be the slave to Corina, the daughter of the Viking Chieftain Erik. While learning on how the Vikings came to Africa from Corina, Tarzan discovers that she is in love with the lawman Sven's son Bjorn much to the objection of Erik. During that time, Tarzan uncovers a plot by the viking Torvald to overthrow Corina's father.
Tarzan's old friend Paul Gregory and his daughter return to the jungle. Paul tells Tarzan that he is here looking for his son Brian who disappeared upon finding the Forbidden City of Ushare located in the extinct volcano Tuen Baka. The next day, Tarzan finds out that three men named Magara, Castelle, and Chabalt (whom Paul encountered at the hotel) are also seeking the map to Ushare in order to steal the father of diamonds. When both groups are captured by the soldiers of Ushare, it is up to Tarzan to free them.
Tarzan discovers an elephants bones on the jungle floor. He investigates further and finds that a band of men have been slaughtering the elephants for their ivory. Tarzan discovers that soldiers led by King Aga of Novard is behind this and his armies are looking for the Graveyard of the Elephants. The Novardians worship the woolly mammoth Bentor (whom they consider a god) and want Tarzan to take them to the Graveyard of the Elephants in order to harvest the tusks there. The king of Novard is able to control the massive beast and use it for evil. Tarzan with the help of his elephant friends destroy the bridge that the Bentar uses in order to stop him from being used for evil purposes.
During a drought, Tarzan finds large footprints and follows them into a hidden valley which contains large trees and vegetation. Tarzan comes to the aid of a giant named Yuri when his father Muro has been imprisoned by the tyrant King Odysseus and that the giants live in fear of Buto (who has been said to be a god in the form of a white rhinoceros). To make matters worse, a dangerous storm is heading to the giants' village of Zoram.
Upon finding a crashed balloon, Tarzan searches for its pilot which leads him to the Valley of Nimmr where he encounters knights that end up taking him to Queen Grenalda. He soon encounters the balloonist Annie Talbot who is a writer. When the queen falls ill and Sir Mallad has Tarzan imprisoned in the dungeon, Tarzan learns from the Queen's Royal Physician Sir Ronald that Sir Mallad plans to steal the throne from Queen Grenalda.
Mr. Senti and his scientist creates a robot duplicate of Tarzan in order to blame the real one for the animal mistreatment so that they can steal the Jewels of Opa. Before long, the jungle animals become mistrustful of Tarzan and attack him on sight. Even N'kima and Jad-bal-jah are unable to tell the difference. Tarzan must now expose the robot Tarzan and thwart the plots of Mr. Senti.
While riding on Tantor, Tarzan saves a boy named Tuck (who mistakes Tarzan as the god Aliat since he resembles him) from Numa. He learns from Tuck that the sorceress Queen Nubia has turned Tuck's father into a baboon causing Tarzan to go to the city of Rashid to confront Queen Nubia. Tarzan later learns that her magic is not as she claims it to be which Tarzan plans to expose.
Tarzan and N'kima follows a boy named Kimo of Nolangi into a crater that leads him to the Land of Darkness with a plan to unite both tribes upon speaking to King Mavor. With help from King Mavor's daughter Nina, Tarzan plans to help Kimo make peace between both tribes while evading the dangers of the prehistoric land of Pellucidar in order to get King Ovan of Nolangi and King Mavor to understand the peace between the tribes.
While working on his garden with N'kima and Tantor, Tarzan sees the mountain of ice about to erupt and has the animals get to safety. The eruption ends up freeing a gigantic Yeti-like ice creature Glakor from the volcano as it soon ends up being targeted by the poacher Norcross and his assistant Phelps.
Upon investigating a strange disturbance in the jungle, Tarzan rescues two slaves named Dimitri and Logos from Grecian soldiers who come from the city of Olympus. Tarzan learns that the slaves were former tournament champions who were defeated by younger challengers and made slaves by Emperor Cronus. Now Tarzan must go up in three challenges in order to free the slaves and make Emperor Cronus see the error of his ways.
The UFO that was previously used by Dr. Krolar returns to the jungle where the robots end up capturing Tarzan. He is brought before Commander Dumay who states that Dr. Krolar and Leera aren't on the mission with him. Commander Dumay plans to use his computer to scan Tarzan's memory in order to learn all of Tarzan's abilities and transfer them to him in order to become supreme ruler of the space fleet.
The Bolmangani Emperor returns and plans revenge on Tarzan by turning a tribe of gorillas against Tarzan. The Bolmangani then go to great lengths by having the gorilla tribe abduct a female archaeologist named Lois as bait so that the Bolmangani can rebuild their city in the Opar Region much to the objections of Lois who claims that the ground there is unsafe.
While walking through the jungle Tarzan discovers a large whale with a harness strapped to him. Tarzan discovers that the whales are being used to create power for the City of Atlantis. The whale takes Tarzan to Atlantis which is deep under the water to investigate. Tarzan learns that the only way to keep the city from becoming flooded is to keep generating power. Tarzan helps discover an alternate power source so that the animals can be freed and the city can be saved.
While enjoying a peaceful day in the jungle Tarzan discovers footprints that lead him a group of Conquistadors. The Conquistadors are searching for the treasure of their ancestors. The treasure that the Conquistadors seek is frozen in a glacier occupied by the Ice people. Tarzan fears that the glacier is going to collapse so he must warn the ice people of the danger of the conquistadors and also get them to leave their home on the glacier before it is too late.
Tarzan stops a stampeding herd of elephants. They tell Tarzan a bizarre story about part of the herd being captured by giant spiders. Tarzan investigates and discovers people operating mechanical spiders. The city is divided into bosses and workers. The workers are ready to revolt and won't release the elephants until society is fixed.
A lost tribe of the Mayans worship their god only to find out he is an alien.
When N'Kima stains his chest with berry juice, a tribe thinks he is a god that is there to save them from the white apes.
Tara, the queen wants to cut all the trees down. Mara, her twin protects the forest as the big rains will wash all their buildings away. Tarzan and Mara flee to the ""haunted forest"". Tara gives chase in spite of her army being afraid.
A lost oriental city in the jungle is controlled by a tyrant using a fire breathing dragon.