In the jungles of British East Africa, the coronation of Melmendi, the queen of the Ashuba tribe, is observed by commissioner Peters, who is about to retire, and his replacement, Connors. As the ceremony concludes, Peters tells Connors about Bulam, the brutal chieftain of the neighboring Yorango tribe, whose marriage proposal Melmendi has just rejected. Noting that he has always kept gin and guns away from the natives, Peters then warns Connors about outsiders selling arms to the villagers and fomenting unrest. Unknown to Peters, Radijeck, a ruthless "slaver," has just escaped from prison and, with his cohorts, Andrews and Herbert Trask, is bringing in a load of illegal rifles to the area. Meanwhile, in a nearby section of jungle, wild man Tarzan learns about Radijeck's escape and, accompanied by his chimpanzee companion Cheetah, races to inform Peters. Later, at his treehouse, a worried Tarzan tells his wife Jane the news about Radijeck, whom Jane unwittingly nursed back to health years before. Tarzan and Jane then discover that the mischievous Cheetah appropriated Peters' confidential notebook, and all three set out the next day for Peters' office in Randini. At the same time, Peters and Connors intercept one of Radijeck's porters in the jungle and become suspicious. To avoid detection, Radijeck orders Trask to impersonate a missionary and claim the porters are carrying Bibles. The ploy fails, however, and to Andrews' and Trask's horror, Radijeck guns down the commissioners. After Radijeck forces Andrews to take Peters' pocket watch, he and a now-wary Andrews and Trask resume their trek. Later, while climbing a steep cliff, Radijeck deliberately drops a boulder on Andrews, breaking his leg. Radijeck and Trask leave Andrews to die, but Andrews crawls into the nearby river and, while grasping some fallen branches, is carried along by the current. Tarzan, Jane and Cheetah, who are traveling by canoe, spot Andrews just as some crocodiles are about to attack him, and Tarzan swims to Andrews' rescue. Tarzan pulls the unconscious Andrews to shore, where Cheetah discovers Peters' watch, an object with which the chimp has long been fascinated. Recognizing the watch, Tarzan and Jane go to see the governor in Randini, after delivering Andrews to the doctor. Although the governor expresses little concern about Peters and Connors' absence, Tarzan is uneasy and decides to investigate. Radijeck and Trask, meanwhile, arrive at the Yorango village and negotiate a deal with Bulam, exchanging guns for gems. Nearby, surrounded by hyenas and buzzards, Tarzan finds Peters' bullet-riddled helmet and deduces his fate. From a tree top, Tarzan then spots Bulam and Radijeck passing by and, swinging from vine to vine, beats them to the safari camp where Trask and some Yorango men are guarding the rifles. Tarzan overwhelms Trask and the guards, but is soon trapped and knocked out by Radijeck. Radijeck and Trask throw the unconscious Tarzan in the river and, after seeing him go over a waterfall while clinging to some branches, conclude he is dead. After receiving their payment, Radijeck and Trask part ways with Bulam, taking a few natives with them as guides. Bulam's armed warriors then attack Melmendi's village, easily overpowering them. Meanwhile, having been washed ashore, Tarzan revives, but must immediately free himself and a baby elephant from a giant, voracious plant. With Cheetah, Tarzan rushes toward Melmendi's village and attacks a spear-wielding Yorango warrior who is chasing an Ashuba boy named Nessi. After instructing Nessi to sneak back to his village and free the bound Ashuba tribesmen while Bulam's men are sleeping, Tarzan rescues the heavily guarded Melmendi. Soon, most of the Ashubas are freed and, seizing the rifles, battle Bulam's warriors. Once the Yorangos are driven from the village, Tarzan vows to capture Radijeck. Radijeck and Trask, meanwhile, wake up to discover their guides have deserted them, and when Trask panics, Radijeck kills him. An exhausted Radijeck eventually finds Jane in the treehouse and tries to force her to help him. When Tarzan suddenly appears, Radijeck grabs Jane and holds her at gunpoint. Radijeck then empties his gun shooting at Tarzan, who is swinging from tree to tree. Unharmed, Tarzan swoops down and knocks Radijeck off the treehouse, killing him. Tarzan and a relieved Jane then embrace, while Cheetah swallows Peters' watch and belches.