The novel picks up soon after where Tarzan of the Apes left off. The year is 1910 and Tarzan is 22 years old. The ape man, feeling rootless in the wake of his noble sacrifice of his prospects of wedding Jane Porter, leaves America 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 two shady characters attempting to prey on them, Nikolas Rokoff and his henchman Alexis Paulvitch. Rokoff, it turns out, is also the countess's brother. Tarzan thwarts the villains' scheme, making them his deadly enemies. Later, in France, Rokoff tries time and again to eliminate the ape man, finally engineering a duel between him and the count by making it appear that he is the countess's lover.