Beau, John, and Digby Geste are three inseparable, adventurous brothers adopted into the wealthy household of Lady Patricia Brandon. When the family's finances dwindle, Lady Brandon is forced to sell her prized jewel—the legendary "Blue Water" sapphire. During a final viewing of the sapphire, the lights go out and the gem is stolen, seemingly by one of the brothers. That night, each brother "confesses" and disappears, with John leaving behind the woman he loves, Isobel Rivers. The brothers join the French Foreign Legion, where Beau and Digby are separated from John and placed under the command of the ruthless Sergeant Markoff. As tensions rise and the Legionnaires plot a mutiny against Markoff, they also face a siege by attacking Arab forces. **Cast:** - Gary Cooper as Michael "Beau" Geste - Ray Milland as John Geste - Robert Preston as Digby Geste - Brian Donlevy as Sergeant Markoff - Susan Hayward as Isobel Rivers - J. Carrol Naish as Rasinoff - Albert Dekker as Schwartz - Broderick Crawford as Hank Miller - Charles Barton as Buddy McMonigal - James Stephenson as Major Henri de Beaujolais - Heather Thatcher as Lady Patricia Brandon - James Burke as Lieutenant Dufour - G. P. Huntley as Augustus Brandon - Harold Huber as Voisin - Donald O'Connor as Beau (child) - Billy Cook as John (child) - Martin Spellman as Digby (child) - Ann Gillis as Isobel (child) - David Holt as Augustus (child) - Harvey Stephens as Lieutenant Martin - Stanley Andrews as Maris - Harry Woods as Renoir - Arthur Aylesworth as Renault - Henry Brandon as Renouf - Barry Macollum as Krenke - Ronald R. Rondell as Bugler Runtime: 112 minutes