Based on Catherine II's diary and directed by Josef von Sternberg, a German princess has her husband Czar Peter murdered and becomes empress of Russia.
The Prussian princess Sophia (Marlene Dietrich) is ordered by her royal father Frederick to marry the grand duke of Russia. The Russian Count Alexei (John Lodge) brings her furs, and in March, 1744 she and her complaining mother travel to Moscow. Alexei kisses Sophia and says he loves her even though it is treason. Empress Elizabeth (Louise Dresser) names Sophia Catherine. Catherine meets the silly Peter (Sam Jaffe) and her ladies in waiting. Alexei apologizes for deceiving her about Peter. The Empress asks her for a son, and Peter and Catherine are wed in an Eastern church ceremony. At the feast Alexei proposes a toast to Catherine, and the Empress retires.
Alexei complains Catherine has avoided him; she says she will be faithful to her husband. Peter tells the Empress he hates his wife. Maria tells Catherine about lovers and that her mother left for Germany. The Empress scolds Catherine and plans to "educate" her. In the hay Alexei kisses Catherine. The Empress cancels a diplomatic dinner and invites men. She intercepts a note from Alexei to Catherine. She orders Catherine to serve the guests and dismisses the servants. Peter drills a hole in a painting, and the Empress warns Catherine not to be her rival with Alexei, telling her of a secret passage. Catherine throws the locket of Alexei out the window and goes out searching for it. Taken by a guard, she kisses him and surrenders to him.
Bells announce that Catherine has a son. The Empress is ill and sends a necklace to Catherine. Alexei is not allowed to see Catherine. Catherine learns that Peter plans to remove her. He drills his troops indoors and threatens her. Catherine sees that Peter has Lizzie back against the orders of the Empress. Lizzie tells Catherine that Peter plans to marry her. People are ordered to pray for the Empress. Catherine is playing with guards and ladies when a bell tolls the death of the Empress. Peter gloats, and has his soldiers arrest people. However, Catherine gains control of the army. She notes the romantic Captain Orloff (Gavin Gordon) and Lt. Dimitri. She takes Alexei's decoration and gives it to Orloff. She invites Alexei to visit her and has him send the others away. Alexei loves her and wants to protect her. She tells Alexei to open the secret door for a man, and Alexei lets in Orloff.
At a banquet Catherine gives bracelets for the poor, but Peter says there are no poor people in Russia. Peter toasts Elizabeth, but Catherine refuses. Peter strips Orloff of his insignia and puts Catherine under arrest. Peter orders people to pray for her. Catherine in a uniform escapes and joins the army pledged to her. She is blessed in a church and rings the bell. Orloff guards Peter and strangles him. Soldiers ride their horses up the stairs of the palace, and Catherine takes the throne.
Generally accurate, this film focuses on the personal life of Catherine during her rise to power. Outstanding music, sets, and costumes adorn the story of her ambitious machinations, seeming to be justified by the portrayal of Peter as an imbecile.