On a rainy night in turn-of-the-century Vienna, Stefan Brand's friends drive him home and tell him they will return to collect him for his duel at dawn. Stefan informs his mute butler John that he has no intention of keeping this appointment, and instructs him to have a carriage ready in an hour. He then finds a letter waiting for him and is astonished by the first line: "By the time you read this letter I may be dead." The letter goes on to describe the writer's memories of first seeing Stefan: Young Lisa Berndle watches in fascination as the beautiful possessions of Stefan, a handsome concert pianist, are moved into the building where she lives. Although she is too shy to speak to him, Lisa quickly falls in love with her new neighbor, who comes to dominate her every thought. When Lisa's widowed mother remarries, the family moves to Linz, and Lisa eventually begins keeping company with Lt. Leopold von Kaltnegger. One afternoon, Leopold begins to speak of the future, and Lisa tells him she is secretly engaged to a musician in Vienna. Her mother and stepfather are shocked, and Lisa returns to Vienna and takes a job in an exclusive dress shop. One night, Stefan notices her standing on the street near his apartment, and is charmed and flattered by her devotion. After dining with her in an elegant restaurant, Stefan gives Lisa a single white rose, then takes her to an amusement park, where they dance until late in the night. They then return to Stefan's apartment and fall into a passionate embrace. The next day, Stefan visits Lisa at the dress shop and cancels their date for that evening, explaining that he must go to Milan for two weeks. He asks her to see him off at the train station, and bids her a warm farewell before joining another woman on the train. Stefan does not call Lisa again, however, and she later gives birth to a son, Stefan, Jr. Back in the present, Stefan looks with pleasure at the enclosed photos of the son he never knew he had. Lisa's letter continues that when the boy was nine, she married the wealthy Johann Stauffer: One night, Lisa and Johann, who treats Stefan's child like his own, go to the opera, and Lisa is stunned to see Stefan, whose musical career has not lived up to his early potential. Greatly agitated, Lisa tells Johann she has a headache and is about to go home when Stefan, who has been watching her from his seat, intercepts her and asks to see her again. Lisa hurries to her carriage, where she finds Johann waiting for her. As they ride home, Johann asks Lisa what she is going to do, and Lisa confesses that she feels powerless before Stefan and believes he needs her. The next day, Lisa puts her son on a train back to school, but they are asked to move after accidentally being seated in a compartment that has been quarantined. As Lisa walks away, bystanders comment that a case of typhus has been discovered on the train. Lisa then buys a bouquet of white roses and goes to see Stefan, as Johann observes her from his carriage. Stefan welcomes her amorously, but when she realizes that he truly has no idea who she is, Lisa leaves in tears. After wandering the streets of Vienna for hours, Lisa goes to see her son, only to learn that he died of typhus during the night. Now very ill herself, Lisa writes that she loves Stefan as much as she always has. The letter suddenly ends, and Stefan finds a note from a nun at the hospital saying that Lisa has died. With tears in his eyes, Stefan remembers the moments he shared with Lisa. Johann and his seconds arrive, and Stefan, ennobled by his sorrow, goes to fight a duel he knows he cannot win, pausing only to pluck a rose from the bouquet Lisa left behind.