Tarzan's amazing ability to establish kinship with some of the most dangerous animals in the jungle serves him well in this exciting story of his adventures with the Golden Lion, Jad-bal-ja, when the great and lordly animal becomes his ally and protector. Tarzan learns from the High Priestess, La, of a country north of Opar which is held in dread by the Oparians. It is peopled by a strange race of gorilla-men with the intelligence of humans and the strength of gorillas. From time to time they attack Opar, carrying off prisoners for use as slaves in the jewel-studded Temple where they worship a great black-maned lion. Accompanied by the faithful Jad-bal-ja, Tarzan invades the dread country in an attempt to win freedom for the hundreds of people held in slavery there.