Polish woman Viktoria Kowalska (Valentina Cortese) has lost her home and her husband in the German occupation of Poland, and has been imprisoned in the concentration camp at Belsen. She befriends another prisoner, Karin Dernakova (Natasha Lytess), who dreams of reuniting with her young son Christopher (Gordon Gebert), who was sent to live in San Francisco with a wealthy Aunt. Karin dies shortly before the camp can be liberated, and Viktoria, seeing a way to a better life, uses Karin's papers to assume her identity. After the camp is liberated, she is interviewed by Major Marc Bennett (William Lundigan), who gets her a place in a camp for persons displaced by the war. She writes to Karin's Aunt Sophia in San Francisco, but receives a cable from Sophia's lawyers that she has died.
Four years later, Viktoria (still going by the name of Karin) is able to travel to New York, where she meets with Christopher's guardian Alan Spender (Richard Basehart), a distant relative of Sophia's. "Karin" intends to gain custody of "her" son, but it becomes clear that Sophia has left her fortune to Christopher when he comes of age. When she realizes that Alan is attracted to her, she realizes that it will be easier to stay in America if she has an American husband. She allows him to romance her, and they soon marry. Alan takes Karin to San Francisco where Christopher meets his "mother" for the first time, and she settles into Sophia's Italianate mansion on Telegraph Hill, where Christopher has lived with Alan and his governess, Margaret (Fay Baker).
Things seem idyllic at first, but tensions begin to mount between Karin and Margaret, who has not only raised Christopher but is also in love with Alan, and resents Karin for intruding on her life. Karin is also alarmed at the presence of a burnt-out, dangerously damaged playhouse overlooking the hill, which Christopher claims to have damaged with an explosion from his toy chemistry set. He and Margaret beg her not to tell Alan, since Margaret never has, but Karin is perplexed to discover that he already knows about it. Karin is pleased, however, to meet Marc Bennett again, learning he is an old schoolmate of her husband's and is a partner for the law firm that handles Sophia's affairs. He is clearly attracted to Karin, but keeps a respectable distance.
Karin investigates the playhouse, but is surprised by Alan while she is in there and nearly falls to her death through a hole in the floor. Alan pulls her up, but appears to be alarmed by her behavior. Soon after, the brakes on Karin's car fail. She escapes unharmed but suspects Margaret of tampering with the car. When she realizes Christopher was supposed to have been in the car with her, Karin comes to believe that Alan is behind the accident, since if Christopher dies Alan will inherit Sophia's money. With Marc's help she begins to investigate, learning that Marc's law firm, which supposedly sent her the cable regarding Sophia's death, has no record of the cable being sent. She also grows significantly more nervous around Alan.
Karin discovers a newspaper clipping in Margaret's scrapbook confirming that the cable was sent three days before Sophia's death: it is a fake, and Alan killed Sophia. She attempts to call Marc but is prevented from doing so when Alan arrives home, and he does not let her out of his sight for the rest of the evening. When he brings in the orange juice that the pair drink every night before bed, she is sure her glass has been poisoned. When he briefly leaves the room, she attempts to call the police, but Alan left the phone off the hook in another room, and calls cannot be made. He returns to the bedroom and coerces her into drinking the orange juice, after which he drinks his own. Thinking himself safe, he confesses to Sophia's murder, and that he has given her an overdose of sedatives in her orange juice. Karin tells him she has switched the glasses and that he has poisoned himself. She tries to telephone a doctor but can't get through. Margaret is awakened by the commotion, and Alan begs her to call a doctor. Realizing that he has tried to kill Christopher as well as Sophia and Karin, she refuses, and Alan dies.
Margaret is arrested for refusing to aid Alan, and it is indicated that she may be charged with his murder. Karin, who has confessed her true identity to Marc, leaves the house with him and Christopher to begin a new life.Richard Basehart as Alan Spender
Valentina Cortese as Victoria Kowalska
William Lundigan as Major Marc Bennett
Fay Baker as Margaret
Gordon Gebert as Christopher
Steven Geray as Dr. Burkhardt
Herbert Butterfield as Joseph C. Callahan
John Burton as Mr. Whitmore
Katherine Meskill as Mrs. Whitmore
Mario Siletti as Tony, the Grocer
Charles Wagenheim as Man at Accident
David Clarke as Mechanic
Tamara Schee as Maria
Natasha Lytess as Karin Dernakova
When the film was released, the staff at Variety magazine, wrote "This is a slow but interesting melodrama about a psychopathic killer, with San Francisco's quaint hill residential sections as background ... [with a] [s]inister mood, and heightened tensions, are well sustained, and performances by Basehart and Cortese convey the drama convincingly. William Lundigan is okay as the attorney who befriends the woman."
More recently, film critic Dennis Schwartz generally liked the film, writing "Robert Wise (West Side Story/The Sound of Music) ably directs this Gothic film noir ... The stark black-and-white photography by Lucien Ballard, the good performances (especially by Basehart) and the intriguing plot developments kept me tuned in throughout even though it was slow going. Of personal interest, Basehart and the Italian actress Cortese met for the first time on this film, and fell in love and married."
NominationAcademy Awards: Best Art Direction - Lyle Wheeler, John DeCuir, Thomas Little and Paul S. Fox; 1952.