Katherine Allenborg, a working girl from the slums, sees the Stylewear Beauty Contest as a ticket to a new life. Although Kathy feels a repugnance toward all men, she decides to use her feminine allure to get what she wants. Upon learning that Sam Lewis, the elderly head of Stylewear magazine, will determine the contest winner, Kathy turns her charms on him. After Sam fixes the contest so that Kathy wins first prize, a trip to Europe, Kathy abruptly dismisses the hapless Sam. On the flight to London, Kathy meets Tim O’Bannion, a struggling television producer employed by the European-based Dowling's advertising firm. Although Tim is attracted to the comely Kathy, she is on the prowl for wealthy suitors and hence shows no interest in the lowly Tim. At the Mayfair Hotel, Kathy, who has changed her name to Kathy Allen, finds a more suitable prospect in her neighbor, successful photographer Larry Buckham. Larry asks Kathy to dinner, but she freezes when he tries to kiss her later that night. The next day, while waiting for Larry in the hotel lobby, Kathy encounters Tim, who insists she join him for a drink. At the bar, Kathy, who possesses no viable skills, asks Tim to help her secure a position at Dowling's. Their conversation is interrupted by the hot-tempered Larry, who insists on immediately leaving the bar. Irrationally possessive of Kathy, Larry proclaims his love and asks her to marry him. As Kathy’s hotel bills mount, she enrolls in secretarial school and then accepts Larry’s proposal. The night after they become engaged, Larry leaves town for a week-long business trip, but before going, suggests that Kathy use his charge at Marshall’s Department Store to buy a wedding dress. When Larry returns to London, he discovers that Kathy has checked out of the hotel, leaving behind thousands of pounds in Marshall’s charges. When one of the store’s executives informs Larry that Kathy has pawned all the merchandise, Larry attacks the man and is arrested and sentenced to jail for assault. Using Tim as a reference, Kathy applies for a job with Stephen Collins, the London head of Dowling's. Smitten by Kathy’s shapely legs, the already married Collins hires her as a typist. While Kathy is working late one night, Collins, out of town on a business trip, phones his secretary to deliver a file. Kathy decides to deliver the file herself, however, and upon finding Collins exhausted from a day of hard work, gets him drunk. After Collins goes to bed, Kathy sneaks into the bedroom, undresses and climbs in. Soon after, Collins promotes Kathy to be his secretary, and the two embark upon an affair. One night, Tim invites Kathy to dinner, and at the end of the evening, they return to her apartment. When Tim nuzzles Kathy’s neck, she experiences sexual passion for the first time in her life. After Kathy laments that she has never felt that way before, Tim observes that she is “twisted up about love.” Soon after, Collins arrives, prompting Tim’s abrupt departure, after which Kathy threatens to break off their affair unless Collins marries her. On a business trip to Paris, Kathy meets Collins’ wife Virginia and discovers that she is the daughter of the firm’s owner, John Dowling. In the ladies’ room, Virginia offers to pay Kathy to end her affair with Collins. Shrewdly calculating, Kathy instead suggests assigning her to a new job in Paris, where Dowling's is headquartered. Soon after Kathy’s arrival in Paris, she manipulates the unwitting Dowling into proposing to her. As Kathy is fitted for her wedding dress, Tim, aware that Kathy loves him, bursts into the room and asks who cut out her heart. Soon after Dowling and Kathy are wed, Kathy receives an anonymous threatening phone call from a man, which is then followed by a menacing letter. One night, Kathy spots a shadowy figure hiding in the bushes, and rattled, removes the pistol from her husband’s desk drawer. Terrified, Kathy pauses in the hallway, and when she sees a shadow approach the doorway, she fires, killing her husband. Kathy’s story that she thought her husband was a prowler is discounted by the police, and once Virginia and the family attorney testify that Kathy only married Dowling for his money, she is arrested and brought to trial on the charge of murder. On the day that Kathy is found guilty and sentenced to death, Tim notices Larry in the crowd outside the courthouse and follows him. After Tim declares that he knows Larry has been stalking Kathy, Tim explains that Kathy’s antisocial behavior stems from an incident that damaged her in youth. Tim then shows Larry a newspaper clipping detailing the adolescent Kathy’s rape by a gang of hoodlums. Touched by Kathy’s ordeal, Larry agrees to go the police and admit that he was the prowler. After Kathy’s sentence is reduced to a three-month term for manslaughter, Tim visits her in her cell and gives her the clipping. When she asks if it is too late for them, he replies he is not sure and walks away.