After six days without rations, a group of Foreign Legionaires who have been made part of a penal battalion and have been imprisoned in an abandoned desert grain pit, slowly perish until only two soldiers remain. As one of the soldiers nears death, he mutters the phrase "stout fellow" and is recognized as John Geste by his American comrade, Otis Madison. The story of John and Otis is then told, beginning with their childhood friendship in the English countryside. Many years later, a now grown Otis returns to England to propose to aristocratic Isobel Brandon, the little girl whom both he and John adored as children. Otis is stunned when Isobel tells him that John joined the Foreign Legion and was unjustly court-martialed and sentenced to a penal battalion. Moved by Isobel's tears, Otis pledges to rescue John, even though he knows that John and Isobel are engaged. After joining the Legion, Otis, who has changed his name to Brown, is shipped to Northern Africa for training. As a first assignment, Otis' battalion is ordered to cross a stretch of the Sahara desert on foot and occupy a French fort. Hit by a brutal sandstorm, some of the recruits buckle with exhaustion and mutiny. Although Otis tries to stop the uprising, he is accused of being the head mutineer and is sent to a penal battalion. Shortly after his arrival, Otis suffers further punishment and is thrown in the grain pit, unaware that John, who calls himself Smith, is his fellow prisoner. As soon as Otis recognizes John, a band of Arabs, lead by an Emir and his half-French mistress, belly dancer Zuleika, rescues them. Although saved from the pit, John is returned to the fort as a prisoner, while Otis becomes a prisoner of the infatuated Zuleika, who informs him about an upcoming Arab revolt. By promising to take her to Paris, Otis gains his release from Zuleika, who then rides to alert the French cavalry. Disguised as an Arab, Otis sneaks to the Legion fort and joins John in the battle. Bravely fighting side by side, John and Otis help save the fort and thereby earn their freedom. True to his word, Otis prepares to leave John and return to Zuleika, but is relieved when he finds the fickle dancer in the arms of his Legion major.