A Nazi officer's mistress helps an American free his mother from a concentration camp.

In 1936, in a concentration camp in the Bavarian Alps, German-born actress Emmy Ritter awaits her death at the hands of the Nazis, only comforted by camp physician Dr. Ditten, who secretly allows her to write a letter to her American-born son, Mark Preysring. Unknown to them, Mark has arrived in Germany searching for Emmy, and after a terrified old friend reveals that she may have been arrested for trying to smuggle money out of the country, Mark goes to the authorities. He learns that Emmy, who had been helping refugees and "enemies" of the German state, has been sent to a concentration camp. Mark then goes to a small Bavarian town in which an old servant of Emmy's, Fritz Keller, lives, but Fritz pretends not to know Mark. One afternoon, a despondent Mark meets Countess Ruby Von Treck, an American-born widow of a German nobleman, who runs a finishing school in her home. Ruby is sympathetic to Mark and asks her lover, Nazi General Kurt Von Kolb, about Emmy and learns where she is confined. Ruby then goes to see Mark at his hotel, but can't bring herself to tell him. Mark begins to fall in love with Ruby, but when he learns that she is friends with a Nazi general, he turns against her. When Kurt reveals that Emmy is about to be executed, though, Ruby invites Mark to meet her at a concert and tells him about Emmy, then advises him to go home. Mark is enraged by her apparent callousness and lashes out at her. After the concert, she introduces him to Ditten, an old friend, who asks Mark to go with him for a drink. Unaware that Mark is Emmy's son, Ditten at first asks him to send some American medical journals to him, but when he realizes who Mark is, he gives him Emmy's letter. When some Gestapo officers come into the café, Ditten leaves, but invites Mark to his apartment the following evening. Back at his hotel, Mark finds Fritz waiting for him, remorseful over his earlier behavior. Fritz admits that he was too afraid to speak to Mark openly, but offers to properly bury Emmy. The next morning, in the concentration camp, Emmy seems to have a heart attack and Ditten pronounces her dead. That night, however, when Mark goes to visit him, Ditten secretly reveals that he administered a drug to Emmy to produce a coma-like state that simulates death. Mark is shocked, but when he realizes that Ditten has given Emmy her only chance, Mark arranges for Fritz to claim the body, then meet him at an inn near the camp. Mark waits, but Fritz does not come, and soon two members of the Gestapo arrive and question him. Suspicious when Mark says that he is waiting for Ditten, they take him to the camp for questioning. Ditten tells the Gestapo that Mark has come for his dead mother's body, and soon Fritz arrives with the proper papers to claim her. Though still suspicious, the Gestapo release the body to Mark and Fritz. After they leave the camp, Mark finally revives Emmy, but because snow and debris on the road blocks their truck, Mark decides to take her to Ruby's house, hoping that she will help. She says she doesn't want to help, but does, even though Kurt has seen Fritz' truck and suspects that something is wrong. The next morning, Ruby obtains a passport for Emmy from one of the girls who is against the Nazis, then sends the rest of the girls off to ski. When Kurt arrives, he is suspicious of Mark, whom Ruby dismisses as someone with a crush on her. She secretly sends Mark away with Emmy and promises to join him later, even though she knows that Kurt will never let her go. After they leave, Ruby prevents Kurt from stopping them by revealing her love for Mark and taunting him, causing him to have a heart attack. As Kurt dies, she promises not to leave him, knowing that Mark and Emmy are free.