Tarzan, feeling rootless in the wake of sacrificing his prospects of wedding
Jane Porter, leaves the United States for Europe to visit his friend Paul d'Arnot. On the ship he becomes embroiled in the affairs of Countess Olga de Coude, her husband, Count Raoul de Coude, and a pair of cruel extortionists, Nikolas Rokoff and his henchman Alexis Paulovitch. Rokoff is actually Olga's brother. Tarzan thwarts the villains' scheme, making them his deadly enemies. Arriving in France, Rokoff makes a number of attempts on Tarzan's life, eventually engineering a
duel between the ape man and Raoul by making it appear that the former is Olga's lover. Tarzan refuses to defend himself in the duel, even offering his pistol to Raoul after the latter fails to kill him with his own. This gesture convinces Raoul of Tarzan's innocence, and since the ape-man finds himself without a purpose, arranges for him to join French military intelligence. Tarzan is assigned to service in
French Algeria. A sequence of adventures among the locals ensues, including another brush with Rokoff. Afterward, Tarzan sails to
Cape Town,
Union of South Africa and strikes up a shipboard acquaintance with Hazel Strong, Jane's best friend. Rokoff and Paulovitch, having stowed away on the ship, finally manage to overpower Tarzan and throw him overboard with heavy weights. Tarzan frees himself and manages to swim to shore. He quickly realizes that the area is in fact the coastal jungle where he grew up. A brave rescue of Busuli, a warrior of the
Waziri tribe, ends with Tarzan being formally adopted as a member. When the Waziri chieftain is killed by encroaching
ivory poachers, Tarzan drives them off. The Waziri then elect him to be their new chief. The Waziri know of a lost city deep in the jungle, from which they have obtained their golden ornaments. Tarzan has them take him there, but is captured by its inhabitants, a race of primitive men, and is condemned to be sacrificed to their sun god.
La, high priestess of the lost city of
Opar, is to perform the sacrifice and speaks the ape language Tarzan learned as a child. When the sacrificial ceremony is interrupted, she hides Tarzan and promises to lead him to freedom. But Tarzan escapes on his own, locates a treasure chamber, and rejoins the Waziri. Meanwhile, Hazel reaches Cape Town, meeting Jane. With Jane is her father, Professor Porter, and her fiancé, Tarzan's cousin
William Cecil Clayton. They are soon invited to cruise up the west coast of
Africa aboard the
Lady Alice, the
steam yacht of another friend, Lord Tennington. Rokoff, now using the alias of "M. Thuran", ingratiates himself with the party and is invited along. The
Lady Alice eventually breaks down and sinks, forcing the passengers and crew into the lifeboats. The one containing Jane, Clayton and "Thuran" is separated from the others and suffers privations. Coincidentally, the boat makes shore in the same general area that Tarzan did. After weeks of near-starvation and misery from sleeping in a crude shelter, Jane attempts to hunt for meat but soon runs into a
lion. Clayton reveals his cowardice and abandons Jane, but the lion is suddenly killed by a thrown spear. Their hidden savior is in fact Tarzan, who does not reveal himself due to anger at seeing Jane with Clayton. Tarzan rejects his humanity, abandoning the Waziri and returning to his original ape clan. Jane breaks off her engagement to Clayton, no longer able to hide her true love for Tarzan. Jane is then kidnapped and taken to Opar by a war party sent to find Tarzan. The ape man learns of Jane's capture and tracks them, saving her from being sacrificed by La, who is crushed by Tarzan's spurning of her for Jane. Clayton tries to go after her but is soon struck down by illness. Thuran discovers other survivors from the
Lady Alice who came to shore some miles away. He leads them away from Clayton and lies that he is the only survivor of his lifeboat. Tarzan and Jane return to Jane's shelter, along the way encountering Busuli who asks him to return to the Waziri. They find Clayton on the verge of death; before dying, he formally passes the title of Lord Greystoke to Tarzan. Tarzan and Jane return to his boyhood cabin and bury Clayton alongside his aunt and uncle. There, they encounter the castaways, who have been recovered by D'Arnot in a French navy vessel. Tarzan exposes Thuran as Rokoff and the French arrest him. Tarzan weds Jane and Tennington weds Hazel in a double ceremony performed by Professor Porter, who had been ordained a minister in his youth. Busuli and the Waziri accept gifts from the French and depart with heavy hearts. The newly christened Lord Greystoke departs for England with the others, along with a sizable amount of treasure from Opar. ==Film, TV or theatrical adaptations==