The picture's supporting players include Johnny Sheffield as "Boy", Otto Kruger, Joe Sawyer, Robert Lowery and John Dehner in an unbilled role as Prince Ameer.

Tarzan receives a request from Jane, who is helping out on the British home front in World War II, to locate a rare plant-derived serum that can save the lives of many service members.

Boy and Cheetah tag along, and soon they are joined by a rambunctious horse and traveling magician Connie Bryce (Nancy Kelly), who has been entertaining Allied soldiers in the region.

Tarzan intends to drop her off and continue his journey, not knowing that she is on a secret mission from Washington to thwart Nazi spies who have infiltrated the kingdom.

Tarzan and Connie quickly run afoul of these devious agents, who manage to frame the two for crimes against the royal family.