Senorita Carmelita Morales, visiting the wife of Major Andrews, U.S.A., is shown much attention by Captain Herbert Richards, with whom she falls in love. Captain Salvada, of the Mexican Army, is a frequent caller at the post. Mildred West also comes to visit Mrs. Andrews, and Herbert at once forgets Carmelita, who is intensely jealous. Salvada attempts to show Mildred attentions, but receives no encouragement, she having taken a strong fancy to Herbert. Herbert catches Salvada cheating at cards and incurs the Mexican's hatred. Salvada leaves the post, swearing vengeance. A troop goes to the target range camp, the major being in command, with Herbert second. Thinking her guests will enjoy a week of camp life, Mrs. Andrews takes the girls to the camp. Carmelita's jealousy has grown to a passion as she witnesses the love between Herbert and Mildred. She chances to encounter Salvada, and asks him to assist her in breaking up the affair. Salvada readily agrees, and writes a love letter, addressed to Mildred, making an appointment for a secret meeting. This letter, Carmelita arranges, shall fall into the hands of Herbert. Carmelita provides herself with a cloak identical with one worn by Mildred, and contrives that Herbert shall see her slipping away from the camp just before the time named for the meeting. Herbert follows the figure he supposes to be Mildred, and witnesses the meeting with Salvada. insane with jealous fury, Herbert follows Salvada. Carmelita, fearing that harm will come to Herbert, in turn follows him, and witnesses his capture by Salvada's men. Carmelita overhears Salvada tell Herbert that be will square accounts by having him shot. She pins a note appealing for aid to the bridle of Herbert's horse, and drives the animal toward camp, she herself going to Salvada and appealing that no harm be done to Herbert. Salvada coldly tells her, however, that, having Herbert safely in his hands, he intends to be revenged, and orders that arrangements be made for his execution. Meanwhile, the horse has reached camp, the note has been read and the troop starts in search of Herbert. Herbert is placed before a firing squad. Carmelita throws herself in front of Herbert, shielding his body, and being herself mortally wounded. An instant later the American troop charges in and the Mexicans are killed or put to flight. Salvada is killed. Carmelita dies in Herbert's arms, paying the price of her jealousy.