A woman spies for Austria during the world war and falls in love with a count, whom she encourages to volunteer for dangerous submarine duty.
When war begins in 1914, Austrian women are urged to serve. In Vienna Elsa Elsbergen (Helen Twelvetrees) volunteers at a hospital but is rejected for lacking references. Captain Muller (C. Henry Gordon) suggests Elsa as a spy, and Major Schmidt (H. B. Warner) asks her to get to know Captain Otto von Lichstein (Lew Cody) to learn if he is a traitor. Otto watches scantily clad women dance and drinks with Elsa, who gives him her address. She came with a colonel but sends him off. A carriage knocks down Elsa, and Count Karl Runyi (William Bakewell) takes her home.
Before Otto arrives, Karl calls on Elsa with gifts brought by three sailors. Elsa tells Otto she will go to his house, but she goes out with Karl instead. Captain Muller tells Major Schmidt that Elsa is not seeing Otto. Elsa dines with Karl, and Otto sees her. Captain Kurt von Hausen insults Elsa, and Karl challenges him. A sailor complains to Elsa's maid Katie (Zasu Pitts) about the duel. Elsa overhears and hurries. Karl tells Elsa that von Hausen was only wounded and kisses her as his ideal. Muller and Schmidt reprimand Elsa, who says she cares about Karl and refuses to spy. Schmidt can't coerce her and dismisses her as only a registered woman.
Karl asks Elsa if she loves him, and she says she does. Karl says he did not volunteer for a submarine mission because of her and suggests they marry; but she advises him to take this chance. Elsa prays for Karl but hopes she won't see him again. In the submarine Karl gets a letter from Elsa that she found someone else. Otto kisses Elsa and asks her to entertain the sailor Heinrich. Tipsy Heinrich tells Otto about the returning submarines. Elsa calls Major Schmidt to come and tries to keep Otto from leaving, pulling out a pistol. Otto struggles with her, and Elsa is shot. Soldiers arrive; Schmidt tells Muller that Otto killed himself, and Elsa is seriously wounded.
After a month the hero Karl calls on Elsa, who is proud of his medal. She tells him there is no other man, and she loves him. Karl tells his mother Countess Runyi (Nance O'Neil) he is going to marry Elsa. The Countess asks Elsa to tell Karl the truth; but Katie tells the Countess that Elsa was commended by the Emperor for catching a spy. The Countess tells Elsa that Karl will be disillusioned in six months; but Elsa reads a letter from her doctor that the bullet will cause her death within six months.
This spy thriller shows that a woman can be as heroic in time of war as a man.