Bob Carter (Ralph Forbes), a seasoned Legionnaire, is dismayed when his younger brother Don (Ben Alexander) joins the same outfit. The brothers' relationship is strained when they both become infatuated with Nina De Bernay (Hala Linda), a cabaret singer who is secretly in love with Bob but is also involved with Sergeant Garcia. Don, ignoring warnings about Nina, is provoked into hitting Sergeant Garcia and is subsequently imprisoned. Nina, with the help of the Arab Sheik Ibrahim-Ul-Ahmed (Roy D'Arcy), helps Don escape. Bob and his friends, Muggsy and Bilgey, pursue them but are captured by the Sheik's forces. The Sheik captures a cache of French machine guns and tortures Don to force Bob, a machine gun expert, to assemble them for the Arab insurgents. Bob seemingly agrees but secretly sabotages all but two of the weapons. Meanwhile, Nina, realizing the Sheik plans a major attack on a French fort, escapes to warn the Legion. During the ensuing battle, the captured Legionnaires turn their rigged machine guns on their captors. In the fight, Don is killed, but not before confessing to Bob that Nina loved him all along and everything she did was to help him. The fort is saved for the Legion