Johnny Weissmuller guides Professor Blakely and his daughter Nora into forbidden Kirundi land, home of the fire-worshipers, in search of missing scientist Ralph Dixon. In addition to finding Dixon worshiped as a fire god, they uncover a treasure of sapphires, rout a party of renegade whites and Johnny rescues Nora from flaming death on a ritual altar just before a volcano erupts molten death.