As a young boy being raised by mountain gorillas after his parents were killed in an African jungle, Tarzan is worried that a fabled monster known as the Zugor will someday attempt to capture him. He is disappointed that he can't run as quickly as the other young apes in his family, and his attempts to prove himself keep resulting in chaos, disappointing Kerchak. When an accident leaves his ape mother, Kala, thinking that Tarzan has died after the gorillas have crossed a ravine, the other apes feel that Tarzan has reached a fitting end. Tarzan believes it’s best for everyone involved if he runs away. Alone in the jungle, Tarzan gets pursued by Sabor the leopardess right to a rocky place known as the Dark Mountain. When the echo of the monster calls, Sabor runs away just as Tarzan is inhabited by two hulking, spoiled gorilla brothers, Uto and Kago, and their controlling, over-protective Mama Gunda, but they fear the Zugor as much as Tarzan does, and when the booming call of the monster again echoes through the valley, the trio flee and Tarzan is able to escape Dark Mountain. He encounters a crotchety old gorilla who at first keeps the boy distant, but Tarzan discovers that this old gorilla is actually the Zugor, who uses hollow trees as megaphones to amplify his voice and pretend to be a monster to scare other jungle creatures away from his territory and food. Tarzan uses this discovery to force Zugor into letting the boy stay with him. Thanks to Tarzan's cheerfulness and helpfulness, Zugor begins to warm up to him as Tarzan continues to try to figure out what he is along with Zugor, but they both promise not to tell anyone. Tarzan's two best friends, Terk and Tantor, come looking for him and Kala also finds out that Tarzan is alive, so she goes looking for him as well. Terk and Tantor encounter trouble in Dark Moutain against Mama Gunda, Uto and Kago but they are able to escape. Then, Terk and Tantor eventually reunite with Tarzan and become best friends once again and leave Dark Mountain in which Mama Gunda, Uto and Kago follow them. Tarzan does not want to return home with them but he reveals that there is no monster, in which Mama Gunda, Uto and Kago hear their conversation and discover Zugor who was the actual monster and he gets himself into trouble. Uto and Kago wreck his tree house for revenge and with that, Zugor blames Tarzan for breaking his promise and runs away, refusing to help in which Terk and Tantor run to go and warn Kerchak. Kala arrives near Dark Mountain and also encounters trouble with Mama Gunda, Uto and Kago in which Tarzan finally realizes what he is supposed to be: a Tarzan, with his own special tricks that no one else can do in the jungle, (which the answer is figured out by Zugor before he returns and becomes friends again with Tarzan). Tarzan is able to use tricks and traps, defeating Uto and Kago as Terk and Tantor try to save Kala as she begins to fall off a cliff, but Tarzan saves Kala just in time whereas Zugor helds hostage on Mama Gunda, but due to their connection and Zugor accidentally telling Mama Gunda that she has “beautiful eyes”, they both fall in love. Uto and Kago return and are schocked to see them together. Tarzan tells Kala that she was right before, and that he is a part of his family and Terk and Tantor again reunite with Tarzan. Tarzan, Kala, Terk and Tantor return to the gorilla troop and the film ends when Kala gives Tarzan a hug and tells him how proud she is of him for rescuing her from the fall and from Uto and Kago, after which Mama Gunda punishes them for destroying Zugor's tree house and orders them that there won’t be any more fighting or wrecking things. Tarzan, Terk and Tantor play a monster game, in which Tarzan is now happy and proud of himself that he knows what he is supposed to be.
