In the Nineteenth Century, John Clayton is married with Jane Clayton and fully adapted to the life in London. He is invited by King Leopold from Belgian to visit Africa but he refuses. However the American Dr. George Washington Williams convinces him to go since he wants to prove that there is slavery in the Belgian lands. Jane also goes with them and out of the blue, the village where they are lodged is attacked by the mercenaries commanded by the evil Leon Rom that works to Leopold. He wants to capture Tarzan to deliver him to Chief Mbonga, who is seeking revenge since Tarzan has killed his only son. In return, Rom will receive a chest of diamonds that Rom will use to pay mercenaries to invade Congo. However Washington saves Tarzan and Rom kidnaps Jane, expecting to be followed by Tarzan that crosses the jungle with Washington to rescue Jane. Will they succeed in their journey?