Flora Hawks is in love with the overseer of Tarzan's African estate. After a search for a legendary city of diamonds, Tarzon races with his pet lion Jad-bal-ja to save Haws from being sacrificed to a lion-god.

The fever for gold corrupts the hearts of men, and Tarzan, the undisputed lord of the jungle, finds himself betrayed. Now, drugged, and at the mercy of the idolatrous denizens of Opar, Tarzan is with his back to the wall, as Flora Hawks, a one-time London maid to Jane Clayton, and her ally, Spanish actor, Esteban Miranda, the spitting image of Tarzan, head to the hidden city of gold. In the meantime, Queen La, the once-powerful High Priestess of the Flaming God, falls from grace, and she flees with Tarzan into the Valley of Diamonds: a secret realm of inexhaustible riches, and the land of intelligent but savage gorillas. Can Tarzan the great, and the mighty, black-maned Jad-bal-ja, his faithful golden-haired lion, restore La to power, and teach the impostor a lesson?—Nick Riganas