Fearing that she is being followed, Judy Allen, a singer from Los Angeles, turns up unexpectedly at the Parisian apartment of her friend, Stella Simmons, and tells this story: Because her singing career in Los Angeles has not been going well, Judy accepts a position as personal secretary for a wealthy man, Eddie Mendies. One evening as she and Mendies are working, a man shoots Mendies through the window. As she drives Mendies to the hospital, he behaves strangely, putting a small key in a wad of chewing gum. Then, giving her a large amount of money held with a money clip, Mendies tells her to lay low for her own safety. From the newspapers, she later learns that Mendies, who dies in the hospital, was a racketeer and jewel fence. The police are looking for the witness to the murder and for missing jewels. Afraid and not thinking clearly, Judy fears that the police suspect her of the killing and that the murderer, whom she cannot identify, is out to get her, so she flees the country. Safe in Stella's apartment, Judy sees that she was foolish not to go to the police, but she knew nothing and wants to remain hidden. Stella invites Judy to stay with her and later introduces her to Don Barlow, an American songwriter hoping for his big break. Don invites Judy and Stella to accompany him to a performance at the famous nightclub, Bal Tabarin . However, during the performance, Judy is frightened by a mysterious man who approaches her, and has Don take her home early. The man, Joe Goheen, later introduces himself to the French police inspector, Manet, as a private investigator looking for Judy. Goheen says he expects that Judy will come to Paris, because he found a postcard sent from Paris in her Los Angeles apartment. However, as Judy has not yet registered with the police, Manet is unable to help. As time goes by, Don shows Judy around Paris and they find themselves mutually attracted. Don tells her that he has not achieved success during his two years in Paris, so must shortly return to his family, who oppose his musical pursuits, in the United States to help run their business. Later, Judy confides to Stella that Don proposed, but she fears his straight-laced family will disapprove of her. Meanwhile, Manet has learned from United States police that Judy is involved with a murder. Skeptical of Goheen's story, Manet has his apartment secretly searched and learns that Goheen has a suspiciously large expense account for a private investigator. At a cafe, Goheen clandestinely meets with Little Augie, his partner in the Mendies murder. Although Goheen did the actual killing, Augie fears that Judy, if interviewed by the police, will identify him, as she knows that he worked for Mendies. Both mobsters are anxious to find her before the police and hope that she can lead them to the key to Mendies' safe, where they believe jewels are hidden. Later, at a restaurant where Stella, Don and Judy are dining, musicians who know Don invite him to play one of his songs and Judy sings along. Hearing them, Jean Dufar, the owner of the Bal Tabarin , invites them to his office the next day and offers them jobs performing Don's music. Meanwhile, at the cafe Goheen frequents, Manet confronts Goheen with what he has learned about the murder and the missing jewels. Goheen now claims he is an insurance inspector, and as they talk, Judy and Stella show up in front of the cafe. Goheen overhears them mention the name of their apartment building, but Manet does not see them. Later, Goheen and Augie break into Stella's apartment and after finding Mendies' money clip among Judy's things, conclude that Judy also has the key to his safe. On the day that Don and Judy are to open at the Bal Tabarin , Manet learns where Judy is staying through the work permit office. When Manet shows up at Stella's apartment to take Judy to the police station for questioning, Stella convinces him to keep her under observation at the nightclub so that she can open the show. That evening, Goheen shows up in Stella's dressing room, but Manet has set up a trap and arrests him. Manet is still unaware that Goheen has been working with an accomplice, until Stella makes a flirtatious remark about "pairs," which sends Manet rushing backstage to Judy's dressing room. There, he apprehends Augie, who is fighting with Don. With the murderers arrested, Manet and Stella settle down for the rest of the show. Watching Stella take chewing gum from her mouth, Manet has a second, serendipitous realization and makes plans to tell the American police to look for the key to Mendies' safe stuck in chewing gum under the dash of Judy's car. As Judy and Don continue their performance, Manet and Stella begin an inspired romance.