Story 1: Korak and Pahkut, his ape companion, set out to hunt while Tarzan and Jane discuss their son’s evolution from Boy into Korak. Tarzan explains to Jane that “Korak” is the closest the apes can come to saying the name “Jack.” Korak and Pahkut spot an empty balloon hung in a tree that must have come from the circus in Nairobi. When they climb aboard the basket, Korak, intent upon studying the craft, does not notice that Pahkut empties all the sand bags overboard in search of food. The balloon drifts loose, with the pair on board, for a great distance, finally clearing the tops of some mountains. In fright Pahkut climbs the ropes and inadvertently pulls the valve cord, causing the craft to crash into the trees beside a mountain lake. They investigate the local tribe by spying over their palisade wall, and Korak sees a young white girl with a small wooden doll being punished by a black woman. After the woman leaves, Korak swoops down to rescue the girl, whose name is Wendy Land. The tribe had burned her home and captured her while her father was away. Mumba returns with a group of warriors and Korak is captured. Meanwhile, Tarzan has tracked the two adventurers and comes upon Pahkut in the forest, lamenting the capture of his son. Tarzan and Pahkut slip over the palisade after dark and knock the guard of the captives’ hut unconscious. As they are freeing the kids, the sight of Pahkut causes Wendy to start screaming, so Tarzan and the group have to escape by fighting their way over the palisade amidst a hail of spears. The next morning, they come upon the hunting party of Wendy’s father, who is anxiously searching for her. Wendy runs to him, as Tarzan and Korak immediately disappear into the jungle.
Story 2: Jane watches Korak and Pahkut wrestle. A messenger seeks Tarzan, who is elsewhere. Korak decides he will respond. Arriving at the village of Chief Kibali, he learns suspicions the white safari is actually "black-birding" for slave labor. Korak enters the safari camp and confronts the three white men. A porter strikes Korak unconscious. Korak is sealed into a barrel. That night Pahkut approaches the barrel by scent and attempts to carry it off, but a porter wakes and Pahkut is grazed by a bullet. The ape drops the barrel and flees. Next morning the trucks depart and eventually enter a cave. Korak and a large number of natives are delivered to a gold mine where Korak is dumped on the ground. He feigns weakness and thirst then makes a break, using a porter as a human shield. Korak escapes and drops the porter, who was wounded. He dives into a river before they can shoot. The river goes underground and Korak struggles to breathe without dashing out his brains. He emerges into a bowl-shaped valley and rests for many hours. Menaced by a belligerent gorilla Korak uses his wrestling tricks to defeat the brute. Korak fashions a spear, hunts, and feasts on a wild hog. He enters a cavern to find a way to free the natives. He meets Bayne and Lasher coming up the other way. Korak hides and watches as they emerge into the valley of the gorillas. The askari with them stands guard as they descend into the forest. The gorillas suddenly attack the white men and savagely beat them to death. Korak comes up behind the askari and grabs his rifle. He marches the askari through the caves until they reach Walleck in the gold mines. At Korak’s command, the natives rise up and one of them hurls himself upon Walleck from behind, causing him to fatally fall on his own gun. Korak disarms the askaris and frees the blacks to return to their homes. He seals the cave entrance with dynamite. He comes upon Pahkut, who has been trailing him, and they set off on new adventures.