An orphaned white child is adopted by Tarzan and Jane, and his relatives come looking for evidence this heir is dead.
A couple with a baby are flying over Africa, but the plane crashes. A monkey takes the baby, and Cheetah throws him to Tarzan (Johnny Weismuller). Jane (Maureen O'Sullivan) orders Tarzan to get coconuts, but he gets a deer for milk. Tarzan names the child Boy.
Five years later Boy (Johnny Sheffield) plays, and Tarzan finds an elephant wounded by a gun. Boy plays with animals and is caught in a spider web; but Tarzan rescues him. Tarzan sees whites shooting Gaboni natives and calls off the natives. Sandee (Henry Wilcoxon), Austin Lansing (Ian Hunter), Mrs. Lansing (Frieda Inescourt), and Sir Thomas Lansing (Henry Stephenson) find the plane and go on to meet Tarzan, Jane, and Boy. They eat, and Jane cooks an ostrich egg. Jane says they buried the baby. Thomas says the Lansings can't inherit a fortune until the son is proved dead. Tarzan plays with Boy in the water as Thomas watches. Tarzan keeps Boy from going over the waterfall. Thomas gives Boy a pocket knife.
Thomas tells the Lansings that Boy is their cousin. Mrs. Lansing suggests they bring Boy back. Austin tells Sandee to confine Thomas. At night Tarzan steals their guns and throws them in a deep pool. Cheetah finds a camera and takes a photo, waking them. Jane refuses to give up Boy. Tarzan tells them to go, but they need guns. To save Boy, Tarzan kills a rhinoceros with a knife. Jane tells Tarzan they must let Boy go, but Tarzan disagrees. Jane suggests they keep Boy and give them their guns back. Tarzan dives for the guns, but Jane leaves him stranded. Jane and Boy go with them. Thomas warns Jane about the Lansings. Austin shoots Thomas. Jane warns them of the Zambilis, who capture them. Jane sends Boy to get Tarzan, and Boy escapes as she is wounded. Boy runs and swims, pursued by a lion and a crocodile. Boy throws a rope to Tarzan, but it fails. Boy gets elephants to push down a dead tree. Tarzan runs and pole vaults over the fence. Then elephants destroy the village. Tarzan finds Jane, and she collapses. Tarzan forgives her. In the final scene Tarzan, Jane, and Boy ride elephants.
This adventure contrasts wild Africa with the devious
violence of greedy Europeans as Tarzan and Jane struggle to keep