Before the First World War, Tania (Greta Garbo) is a Russian spy who has a love affair with Austrian Captain Karl von Heinersdorff (Conrad Nagel) in order to obtain secret plans that he possesses. Despite falling in love with Karl, Tania still steals the plans. Karl is court-martialed and jailed, but his uncle (Albert Pollet) helps him escape and Karl goes to Russia to find Tania. When he finds her, he discovers that she truly loves him. Tania then works to support Karl's cause and betrays her spy chief, General Alexandroff (Gustav von Seyffertitz), by obtaining papers that Alexandroff received from an Austrian traitor and giving them to Karl. When Alexandroff discovers this, Tania is forced to shoot him. She and Karl then flee Russia and go to Austria to clear Karl's name and start a new life together.