Letter from an Unknown Woman

In Vienna about 1900, the decadent pianist and wolf Stefan Brand is challenged for a duel by a deceived husband. He arrives in his apartment and tells his dumb butler John that he intends to leave Vienna to avoid the scheduled duel, and John delivers a letter from an unknown woman to him. He reads the letter written by his former neighbor Lisa Berndle where she tells that she was a teenager when she develops a platonic love for Stefan, who is a promising pianist compared to Mozart. Lisa worships his performances on the piano, but she moves with her family to Linz. Later she returns to Vienna as an independent young woman, having a brief affair with Stefan, who travels to Milano promising to return in two weeks. Years later, she meets him again at the opera and her passion arises again, believing that Stefan remembers her...