Sergeant Barnes, a U.S. Army scout at a desert post, befriends and comes to love Alice Corbett, a widow with a little daughter, who launders and cooks at the post. At a ball celebrating Colonel Sears' birthday, Barnes sees Dr. Deschamps, the Army physician, flirting with Mrs. Sears. After Barnes sees them riding together, he demands that Deschamps resign or face exposure. When Sears sends Barnes on a mission across the desert, Deschamps poisons his horse's sugar, while the half-breed Unitah, whom Barnes knocked down for mistreating a horse, follows Barnes and as he sleeps, replaces his canteen water with sand. Driven insane by thirst and the circling buzzards, Barnes wanders until he falls at a railroad track, where he is rescued by a train crew. After he recovers from amnesia upon seeing the American flag, Barnes wires his post. Deschamps and Unitah flee, but Barnes finds them and they fight. After soldiers shoot Unitah and arrest Deschamps, Barnes is commended for bravery. He then marries Alice.