A major undertaking for M-G-M and the first non-documentary production to be filmed in Africa, Trader Horn starred the veteran Harry Carey in the title-role, Aloysius "Trader" Horn, a white explorer in Darkest Africa. Travelling up a heretofore undiscovered river, Horn and his young companion Peru (Duncan Renaldo) experience strange and disturbing behavior from the native population. As Horn explains: "When the Masai and the Kukua Tribes get together, the devil is certainly involved." Along with their native tracker Renchero (Mutia Omoolo), Horn and Peru encounter Mrs. Edith Trent (Carey's wife Olive Golden), whom Horn calls "the bravest woman in all of Africa," and who is determined to trek above the perilous Opanga Falls in search of her missing daughter Nina, rumored to be the captive of the Isorgi tribe. Although refusing to let Horn and Peru accompany her -- because "the presence of white males with guns will only startle the warriors into violence" -- Mrs. Trent consents to let the men follow her at a distance. Horn discovers the elderly woman's slain body soon after and pledges to continue the search for her missing daughter. After encountering sundry ferocious wildlife fauna along their way, our heroes finally locate Nina (Edwina Booth), who instead of being kept prisoner turns out to be a sadistic white goddess ruling the tribe with an iron fist. Having immediately sentenced the intruders to the stake, Nina has a change of heart in the last moment and agrees instead to accompany them back to civilization. After braving a series of hair raising perils, during one of which Ranchero sacrifices his life to protect his charges, the group are shown to safety by a tribe of pygmies.