Travellers near Zambezi are being killed, apparently by leopards. The commissioner asks Tarzan to look into the matter. Tarzan, Jane, and Boy take in Kimba, a boy who claims to have become lost in the jungle. Kimba is the brother of Queen Lea, leader of a leopard cult. She has dispatched him to spy on Tarzan.
Kimba has a goal of his own: to take the heart of Jane a deed that would make him a warrior in the eyes of the cult. The Leopard Men wear leopard skins that form a cowl and cape, with iron claws attached to the back of each hand. Queen Lea wears a headband, wrist bands, ankle bands, halter top and miniskirt made of leopard skin. As "Variety" put it: "She displays plenty of what it takes to stir male interest and handles her acting chores adequately." She works her followers into a frenzy in an underground chamber, "These skins are your disguise. These claws are your weapons. Go not as men, but as leopards. Go swiftly, silently."