On the eve of World War I, Suzy Trent, an American show girl working in London, loses her job when the show closes and resolves to marry an aristocrat. One day, she is bumped by a chauffeur-driven car, and the "lord" offers to give her a ride home, but she soon discovers that he is actually a poor inventor named Terry Moore. Despite Terry's poverty, Suzy falls in love with him, and accompanies him to a factory, where each night he secretly works on his new invention, an airplane stabilizer. When his employer, Mrs. Schmidt arrives, she angrily tells them to leave but does not see Suzy, who has hidden. Suzy then hears Mrs. Schmidt and another woman and man talking in German, but does not understand them. When Terry returns for Suzy, Schmidt sees him and, worried that he knows that they are spies, sweetly offers him a job as plant manager to keep him quiet. An elated Terry then proposes to Suzy, and they quickly marry. When they return to her place to pack, Mrs. Schmidt's female cohort follows them and shoots Terry. Terrified because Terry appears to be dead and another tenant calls the police to report that Suzy killed him, she runs away. She then goes to Paris to see her friend Maisie and gets a job as a singer in a cabaret. There she meets Andre Charville, an "ace" flyer who is attracted to her. They fall in love that night and immediately marry. One week later, Andre takes her home to his father, the Baron Charville, who is accustomed to Andre's impulsiveness, but is not happy with the marriage. When Andre's leave is suddenly cancelled, Suzy stays at his father's house. Soon her kindness and devotion to Andre impresses the baron and they become very fond of each other. While Andre is acclaimed as a national hero, it becomes apparent that he has been having affairs with other women, particularly a certain Madame Diane Eyrelle. Suzy is miserable without him, and when he gets a leave, his father has to beg him to be kind to Suzy. After Andre returns to the front, Suzy pretends to be happy for the baron's sake and each day reads the supposed contents of Andre's letters to her, even though he never writes. Meanwhile, in England, Terry, who was only wounded in the shooting, has become successful as the inventor of the stabilizer. As part of his work, he is asked to fly some planes over to Andre, unaware of his connection to Suzy. Because Andre has been wounded, Suzy goes to visit him and she and Terry run into each other in the hospital. They are both shocked, but pretend not to know each other. She later feels that she must tell Andre eveything. When she goes back to Andre's room, she sees him kissing someone, but does not know that the woman is Mme. Eyrelle. Suzy then goes to Terry who is initially angry, but soon promises to set her free from their marriage. When he meets Mme. Eyrelle, neither can remember where they have met before, but later, when Suzy sees a picture of Mme. Eyrelle in a magazine, she recognizes her as the woman at Mrs. Schmidt's factory. Suzy goes to Terry with the information and he agrees to help her. They then go to Andre, who has recuperated and is visiting Mme. Eyrelle's chateau. When the spy is exposed, one of her followers shoots Andre. Andre then asks Terry to fly his planned mission for him and begs for Suzy's forgiveness before he dies. Terry's mission is a success, but returning to the airfield, his plane crashes near the chateau. Knowing that the baron would be heartbroken to find that his son died because of his involvement with a spy, Suzy convinces Terry to place Andre's body in the plane and make it appear that he has died heroically. A short time later, at a ceremony honoring Andre, a German aviator flies overhead and drops a bouquet of flowers, after which Terry escorts Suzy back to Paris.