During World War I, young Dorothy Grant comes home from finishing school and informs her parents that she is going to contribute to the war effort by organizing a "Girls Aviation Corps". She has uniforms made and hires a veteran of the Spanish-American War to teach her "cadets" military routines and drills. Her father owns a munitions factory and is always telling her to be on the lookout for spies. She convinces herself that the family butler, Williams, is a spy because he cuts his grapefruit in an odd way. It turns out that Williams isn't a spy but the people whom Dorothy least suspects are in fact spies, and they discover that Dorothy knows the password to get into the factory after hours.