Plot

During a rebellion in Mexico, Nina Garcia, a diplomat's daughter, is forced to become a spy for the revolutionaries. She works as a nurse in a military hospital and steals papers for the rebels, but officials finally discover her involvement in enemy espionage. Just as soldiers arrest her, she performs an experiment on herself, hoping to prove the worth of Dr. Ralph Hamlin's serum for gangrene. Unimpressed by her bravery and unmoved by Ralph's pleas for a pardon, the government orders her shot after her recovery from the injection. Finally, United States troops arrive and save Nina from execution.—Pamela Short

General Torrenti and General Nomonza are leaders of rival military factions in Mexico. Senor Garcia, who is the Nomonza diplomatic agent in Washington, has two daughters, Nina and Camilla, who live with him, and a son, Carlos, a lieutenant in Nomonza's army. Nomonza suspects Senor Garcia of treachery and sends Jose, his favorite spy, to Washington, with the orders of dismissing Garcia and charging him with treason. The unjust accusation so humiliates Garcia that he dies of heart failure. Garcia's two daughters return to the family estate in Mexico and Nina undertakes to assist her brother Carlos in the service of Nomonza, believing that their efforts may clear the Garcia name from disgrace. Jose, always willing to lend his sympathies to the stronger faction, has meanwhile joined the Torrenti forces, and one of his missions is to capture Carlos Garcia and take from him an important message which he is known to be conveying for Nomonza. The spy leads his forces to attack the Garcias at their home, and while Jose attempts to force his attentions upon Nina, other Mexican brigands attack Camilla with the purpose of carrying her away. Nina pleads with Jose that her sister may be spared and finally consents to his demands that Nina shall become a spy for Torrenti, while her sister is held as hostage by Jose's mother. Nina is forced, by Jose, to enter the Nomonza military hospital under the guise of a nurse. There she meets Dr. Ralph Hamlin, an American military surgeon. While in the hospital, Nina is forced by Jose to proceed on various errands and secures a number of important documents which she turns over to the Torrenti spy. Ultimately Nomonza discovers Nina's true occupation. Just as he is about to arrest her, the girl herself imposes an experiment upon her own system whereby she hopes to prove the value of Dr. Hamlin's serum. Nina remains in the hospital for some time lingering between life and death. Jose, moved by conscience, permits Camilla to visit her sister's bedside and she remains there until Nina ultimately recovers sufficiently for Nomonza to arrest her and order her execution. In the meanwhile, Nomonza has executed Jose and when Nina is led forth to be shot, Dr. Hamlin realizes as he has never done before how necessary the girl has become, not only as an assistant, but because he now realizes he is in love with her. The American's pleas for clemency are unavailing and the firing squad is ordered to execute its mission. While these events have been taking place Mexican bandits have raided an American town and involved the United States Army in the settlement of the difficulty. Thus it is that the American troops are approaching the town where Nomonza has his headquarters on the day that Nina is condemned to be shot, and at the moment the firing squad is to execute Nomonza's orders, a brilliant cavalry charge brings the soldiers of Uncle Sam to Nina's rescue.—Moving Picture World synopsis