The Green Goddess is a totem worshiped by the primitive natives of a lost city deep in the jungles of Guatemala. It contains both a fortune in jewels and an ancient formula for a super-explosive which could threaten world safety in the wrong hands. From Africa, Major Martling and Ula Vale launch separate expeditions to find the Goddess and place its secrets in safe hands. Ula's fiance died in an earlier attempt at the same goal and she has taken up the trail in his memory against the advice of her lawyer, Hiram Powers, who covets the Goddess for himself and sends Raglan, a mercenary, to get it for him. Aboard their ship to Guatemala is Lord Greystoke - aka Tarzan - on a mission to find his old friend, d'Arnot, whose plane crashed in the vicinity of the same lost city. Tarzan joins forces with Martling, and they reach the lost city in time to save d'Arnot, but lose the Goddess to Raglan. Ula joins Tarzan and Martling in pursuit of Raglan, whence they must contend with the perils of the jungle, Raglan's henchmen, and a party of primitives from the lost city sent to retrieve the Goddess...