The scene is set in St. Petersburg, Paris, and Switzerland.

The home of Count Vladimiro Andrejevich in St. Petersburg. The beautiful princess Fedora Romazov is engaged to Count Vladimir, son of the dreaded St. Petersburg police chief. On a chilly Christmas evening, first Vladimir’s servants and later Fedora herself are impatiently awaiting the count’s return. Suddenly he is rushed in on a stretcher seriously wounded by gunshot. De Siriex, a French diplomat, helps policeman Gretch interrogate the servants for clues as to what could have transpired, and suspicion points to one Loris Ipanov. Fedora pledges her life to avenge this purposeless crime, but in spite of her prayers and entreaties, her fiancé expires.

Princess Fedora’s home in Paris. Fedora is giving a party together with her friend Olga ostensibly to introduce to society one Boleslao Lazinski, celebrated Polish concert pianist and nephew of Chopin. But Fedora’s real plan is to entrap the suspected murderer, Loris Ipanov, into a confession. While Lazinski performs for the guests, Fedora unwillingly finds herself attracted to Loris. Ignoring her heart, she interrogates the suspect until he finally admits to the murder of Vladimir. The party is ending, as Loris agrees to return in an hour and explain further. Fedora hastily sends a letter to the St. Petersburg police chief which cites Loris as his son’s murderer. When Loris then arrives, he explains instead that the murder was in self-defense, and shows a letter which proves that his own wife had been actually having an affair with Vladimir. When Fedora realizes that she had been duped by her late fiancé, her blood-thirsty anger blossoms into grateful love for Loris, now become her avenger.

The Alpine villa of Fedora and loris near Berne. The two lovers are living together happily in Switzerland. De Siriex shatters Fedora’s idyllic world by bringing her tragic news. As soon as he received Fedora’s accusation, Vladimir’s father had arrested Loris’s brother. But the poor young man died in prison, and, upon hearing this news, Loris’s mother died of shock. Realizing the fatal consequences of her act, Fedora prays. Loris returns home, opening a letter from his friend Dr. Boroff. He discovers that his mother and brother are dead, that his accuser was a Russian noblewoman living abroad, and that Borov is arriving soon to tell him the spy’s name. At this last news Fedora panics, and begs Loris to show mercy to the unknown accuser. Loris asks her to assist him in discovering the spy, and slaying her. Pushed to the breaking point, Fedora swallows poison, revealing her true identity. Loris is moved by her act of self-sacrifice, and offers his forgiveness. It is too late.