In attempting to track Jane, Tarzan has come to a hidden valley called Pal-ul-don filled with dinosaurs, notably the savage Triceratops-like Gryfs, which, unlike their prehistoric counterparts, are carnivorous and stand 20 feet tall at the shoulder. The lost valley is also home to two different adversarial races of tailed human-looking creatures: the hairless and white skinned, city-dwelling Ho-don and the hairy and black-skinned, hill-dwelling Waz-don. Tarzan befriends a Ho-don warrior, and the Waz-don chief, actuating some uncustomary relations. In this new world Tarzan becomes a captive but so impresses his captors with his accomplishments and skills that they name him Tarzan-Jad-Guru ('Tarzan the Terrible').Having been brought there by her German captor, it turns out Jane is also being held captive in Pal-ul-don. She becomes a center-piece in a religious power struggle that consumes much of the novel until she escapes, after which her German captor becomes dependent on her due to his own lack of jungle survival skills.With the aid of his native allies, Tarzan continues to pursue his beloved, going through an extended series of fights and escapes to do so. In the end success seems beyond even his ability to achieve, until in the final chapter he and Jane are saved by their son Korak, who has been searching for Tarzan just as Tarzan has been searching for Jane.
