The early 1960s. An ocean liner.
Liese and her husband Walter, a German diplomat, are aboard a cruise liner headed to Brazil. On deck she sees another passenger who she recognizes as someone she once knew, Marta, but believes had died. Liese is suddenly overwhelmed by emotions and surging memories that she confesses to her husband that she was an SS Overseer at Auschwitz. Walter fears a diplomatic scandal. Liese asks the ship’s steward to find out who the woman is and where she comes from. When he soon reports back that she is a British citizen, Liese and Walter are relieved and head to the ship’s ballroom to dance.
1944. Auschwitz Concentration Camp.
Again overcome with the horrifying memories of her own past, Liese’s thoughts fly to Auschwitz. She recalls the inhumanity of her fellow SS Officers there.
Marta is among the prisoners. Liese enlists her to help manage the other prisoners, among them women from many countries and religions, and cultures, all of whom are deeply suffering physically and spiritually in the camp. A Kapo finds a note in Polish and Marta is ordered to translate it. Marta recognizes it as a message between members of the resistance and therefore purposefully mistranslates it as a love note to her fiancé Tadeusz in order to protect the sender and recipient of the secret message.
Back on the ship, Liese tells Walter that it was very hard to treat the prisoners with dignity and respect when they so brazenly lied to their captors.
1944. Auschwitz Concentration Camp.
Liese memories of her experience in the concentration continue. The SS Commander is visiting the camp and has requested that a prisoner play his favorite waltz for his enjoyment. Tadeusz, a prisoner, has been selected to play, and a violin is retrieved from the confiscated goods of the newly arrived prisoners. When is ordered to come collect his instrument, Tadeusz unexpectedly meets Marta and they recognize each other. In an instant, they fall into each other’s arms and recall their lives before the camp – they were in love and engaged to be married. Their short meeting is interrupted by Liese, who notices but allows them to talk privately in violation of the regulations.
Later, as Tadeusz makes jewelry for SS officers in a camp workshop, Liese visits him. In one of the medallions Liese sees a Madonna with the face of Marta. In an effort to do something kind, Liese offers to let her set up a meeting between him and Marta, but Tadeusz refuses, not wishing to be indebted to Liese, or possibly endangering Marta in any way.
As Marta celebrates her 20th birthday, Liese informs her that Tadeusz has refused to meet her. Marta is certain Tadeusz had a good reason.
The wardens read out a list of female prisoners sentenced to death. Although Marta´s number hasn’t been called she wants to join the doomed. But Liese stops her: Marta will indeed be punished, but first she must hear Tadeusz’s concert.
The ocean liner.
Liese and Walter decide to forget about the past. Liese cannot be guilty for what happened as she was only doing her duty. She tried to be kind and compassionate, but the prisoners rejected her. She is therefore not responsible for her actions. They go out to dance. Liese suddenly sees Marta speaking the band, apparently making a request for the next song. To Liese’s horror, the band begins to play the Auschwitz Commander’s favorite waltz, and the memories flood back…
Officers gather for the concert. Tadeusz is ordered to play the Commander’s favorite waltz but instead he quietly rebels, choosing instead to play Bach’s Chaconne. The music breaks off abruptly when officers smash Tadeusz’s violin and drag him to his death.
The Passenger is alone in her cabin. Remembering the past, she hopes that none of the victims will ever be forgotten.