Two leopard men take the Professor to the forgotten city of Opar, where Queen La is hoping for a king. She refuses the Professor and has the leopard men do what they wish with him. When Tarzan and the others find out, they all head for Opar, just in time to save the Professor. However, after seeing Tarzan, La falls in love with him and plans to get rid of Jane.

The leopard men attack the treehouse and, rather than retrieving Tarzan (as the gang expects), make off with Jane, and gas the others. Once conscious, Tarzan, Tantor, Terk and the Professor set off for Opar to rescue her, only to find Queen La, staffless and at the mercy of a leopard, begging for help. Despite the Professor's warning, Tarzan intervenes and forges a temporary alliance with La to free his wife from La's rebelling minions. However, he is unaware of the true intentions of La and the leopard men.

While the gang is setting up a surprise croquet game for the Professor, Jane encounters an ill-looking fawn. Upon touching the fawn, the soul of Queen La enters her body. Failing to return to Opar by herself, La turns to Tarzan, who senses something wrong right away. Instead, she turns to Dumont for help. Can the aid of Usula, the Waziri elder, bring Jane back before La retrieves her staff and brings Opar to life again?