In Wasabi, Africa, anthropologist Dr. Linda Roberts pleads with Commissioner Kingston for a permit and government assistance to lead a safari into the jungle to find the rumored land of the Giant People. When Kingston turns down her request, Linda insists she will go alone. Kingston's secretary recommends she seek out guide Jungle Jim to help her on her quest. On Gamba Lake, Linda and her hired men are attacked by a hippopotamus, and the men abandon Linda, who makes it to shore alone. Linda is then stalked by a panther, but Jungle Jim has heard the earlier attack and comes to her rescue. Later at Jim's camp, Linda explains her purpose but before Jim can respond, he is summoned by a local ancient wise man known as the Old One. Jim agrees to take Linda along, but on the river, their boat is attacked by the hippo, which Jim kills after a fierce underwater battle. At the camp of the Old One, Kingston awaits and explains to Jim that unscrupulous traders seeking ivory are murdering a herd of elephants trapped by flood waters in a remote part of the jungle. Kingston requests that Jim show him the route into the land of the Giant People, which the commissioner believes would provide the only means out of the jungle for the elephants. Jim refuses, noting that the waters will recede eventually and that the Giant People are far too dangerous to risk disturbing. When Kingston reveals that his men have captured two of the Giant People, Jim warns him not to release them. Returning to camp, Jim spots local natives carrying ivory tusks and follows three natives to a cave, where he captures two of them. At the encampment of hunter Fred Lewis and his ward Denise, meanwhile, trader Quigley complains that Lewis' ivory shipment is short. Just then Jim arrives to report the ivory theft to Lewis. Quigley demands more ivory, but Lewis reminds him of the legal restrictions. Back in Wasabi, Lewis, Denise and associate Doc Edwards meet with Kingston and volunteer to free the elephants by following the captured Giant People back to their land. When Lewis cautions that the Giants may be dangerous, Denise suggests Edwards drug them to reduce the risk. Later at their camp, Denise and Edwards discuss their plan to get more ivory to sell to Quigley without Lewis' knowledge. When Edwards attempts to inject the female Giant with the drug, the male breaks out of his cage and, although wounded by a guard, escapes into the jungle. Kingston and his soldiers are alerted and search for the Giant. Working alone at Jim's camp, Linda is nearly attacked by the Giant, but Jim arrives and fights him off, before the creature flees back into the jungle. Jim pursues, with Linda and Jim's pet chimpanzee Tamba trailing. At the Lewis camp, the Giant returns and frees his mate, who disappears with him into the jungle. Lewis then overhears Denise making arrangements with a native Zulu and demands an explanation. When he learns that Denise is only after the ivory, he threatens to tell Kingston, but Denise orders the Zulu to kill Lewis. When Jim reaches the camp while following the Giant, Edwards knocks him out. Denise suggests that Edwards use truth serum on Jim to force him to reveal the location of the land of the Giants. As soon as Kingston arrives at the camp, Denise and Edwards tell him that Jim is guilty of Lewis' murder. Kingston arrests Jim, who is bound and gagged, while Denise, Edwards and the Zulu follow the escaped Giants. That night Linda and Tamba come into Kingston's camp and free Jim. The three then follow Denise and Edwards to the edge of the land of the Giants and discover the elephant herd. Coming upon the Zulu, Jim demands that he lead them to Denise and Edwards to prevent additional slaughter of the elephants. When Denise and Edwards are threatened by the male and female Giant, Denise kills the female, sending the male on a rampage. Jim defends the group, just as Kingston and his men arrive to re-arrest him. Tamba creates a diversion, allowing Jim and Linda to escape, and they follow the fleeing Zulu. After recapturing the native, Jim and Linda bring him to Kingston to confess that he murdered Lewis on Denise's orders. When the Zulu attempts to escape, he is killed by Kingston, but the shot starts an elephant stampede, which Jim redirects out of the secret pass. Denise and Doc, attempting to flee the stampede, run directly into Jim and Linda. Jim subdues Edwards, while Denise evades Linda, only to be captured by the male Giant. After a struggle, the two fall to their deaths from a cliff. Later, Kingston apologizes to Jim, and Linda declares that she has no further interest in seeing more of the Giant People.