Brothers Beau, John and Digby Geste join the Foreign Legion, where they fall under the rule of tyrannical Sergeant Markoff. Beau and John are assigned to Fort Zinderneuf, where Markoff tries to break their spirit, aware of a dark family secret concerning a fabulous jewel one of them carries. As tensions rise, Arabs attack the fort and rivalries must be thrown aside in a desperate battle for life.

Rose Manning swears revenge for the unjust slaying of her father by Inspector McArthur. Five years later, as a nightclub hostess, she is sought by Chuck Gaines, secretly a bootlegger, but she centers her attentions on young Jimmy Carter, who, she learns, is the son of McArthur.

An American pilot with a top-secret invention is kidnapped by foreign agents.