This semi-film within a film opens in the office of producer George Jessel (Himself), who never saw a camera he couldn't get in front of, who is holding a story conference to determine the screen treatment for the life of Eva Tanguay (Mitzi Gaynor), and Jessel is unhappy with what the writers present him.He tells them to look up Eddie McCoy (David Wayne), Eva's one-time partner, for the real inside story on the lusty and vital Eva. Eddie's version is that he discovered her working as a waitress in an Indianapolis restaurant in 1912, wherein singer Larry Woods (Bob Graham) and his partner Charles Bennett (Oscar Levant) get into a fight over her and both land in the hospital, and McCoy convinces the manager to put Eva on as a single to fill their spot. She flopped, but McCoy arranges for Bennett to be her accompanist, and she went out of his life. The writers look up Bennett, now head of a music publishing company, who says McCoy's story is phoney, and it was Flo Zigfeld (Wilton Graff) who discovered Eva for his Follies. Then Jessel's staff comes up with a letter from Larry Woods with another version.

Twentieth Century-Fox film producer George Jessel is frustrated by the task of making a film about the life of vaudeville star Eva Tanguay, whose madcap antics and signature song, "I Don't Care," earned her the nickname "The I Don't Care Girl." One day, Jessel reviews a script submitted by writers Keene and Lawrence and tells them that they are no closer to revealing the impetuous Eva's true nature than before. Jessel instructs the writers to interview Eddie McCoy, Eva's first partner, and when they question the former song and dance man, he tells them how he met Eva: After Eddie's wife dies, he begins performing alone, but is warned that he is not as good as a solo. Wandering the streets, Eddie stops at a small restaurant and is charmed by the impromptu singing and dancing of Eva, who works there as a waitress. After Eva is fired for breaking dishes, Eddie persuades her to join him, and during the next few weeks, teaches her his routine. Eva and Eddie are a hit during their first appearance, although Eva is distracted by her attraction to singer Larry Woods. Larry's partner, pianist Charles Bennett, is jealous, as he is also infatuated with Eva, and informs her that Larry is married. Infuriated, Eva pours a cup of coffee on Larry before he can explain, then tours the country with Eddie, although he can tell that she misses Larry. By the time they reach New York City, Eddie's weak heart prohibits him from working and Eva continues alone. Eva wows the crowd with her energetic performance, and there Eddie's story ends. When Keene and Lawrence repeat the information to Jessel, he orders them to meet with Bennett, who is now a music publisher. Bennett laughingly tells the two writers that the story Eddie told them was entertaining, but not true. After informing them that Eva had been a café performer before she met Eddie, Bennett relates what really happened when she and Eddie came to New York: At the Alhambra Theater, Eva begs the drunken Eddie to sober up before their performance. Their bickering bothers headliner Stella Forrest, and she complains to Mr. Malneck, the theater's owner. Malneck orders Eva to play that afternoon's show alone, and when she states that she needs an accompanist, he takes her to Stella's room, where she is conferring with Bennett. Eva and Bennett are delighted to meet again, and he stages a sophisticated number for her, which is so popular that Stella orders Malneck to fire Eva. Larry has brought impresario Florenz Ziegfeld, Jr. to see Eva, however, and he hires her for his Follies. Later, when Larry and Eva are rehearsing their Follies number, he confesses that he is trapped in a loveless marriage to his money-grubbing wife Polly, but that he has fallen in love with Eva and would marry her if he were free. Softened by his declaration, Eva encourages Larry to get a divorce and promises to marry him. Ziegfeld's touch makes Eva a star, and later, she becomes the headliner of the Follies. On the opening night of Eva's new show, Larry tells her that his divorce will be final soon, and informs her that he will be playing his new operetta for a "big producer" that evening. Later, however, Bennett inadvertently reveals that Larry is auditioning his operetta for Stella, whom Eva has never forgiven for getting her fired. Overcome by her temper, Eva refuses to see Larry, but when she learns that the United States has entered World War I, she realizes that her own problems are insignificant and tells Bennett to arrange a meeting with Larry. Before Bennett leaves, however, Eva learns that Larry will be singing with Stella at a benefit show. Again acting without thinking, Eva arranges to have a man armed with tomatoes in the audience during Stella and Larry's performance. Much to Eva's dismay, Larry has enlisted in the Army and appears in his new uniform, and the shocked audience boos when Eva's helper hits Larry with a juicy tomato. Horrified by what she has done, Eva goes into hiding, and Larry reads that she has announced her retirement. Determined to rouse Eva, Larry asks Eddie and Bennett for help, and they persuade her to visit him by implying that Larry may be shipped overseas soon. At the Army camp, Larry is preparing a service benefit show, but when Eva appears and tearfully bids him farewell before his supposed departure for France, he cannot bring himself to tell her the truth. Eva learns the truth from Larry's lieutenant, however, and a disgusted Eddie and Bennett walk out as Eva and Larry quarrel. When Bennett finishes the story, he confesses that he does not know what happened to Eva and Larry. Jessel is perturbed when Lawrence and Keene tell him that the movie will not have a happy ending, and when his secretary tells him that a gentleman who has been trying to see him for weeks has appeared yet again, Jessel grudgingly admits him. The man turns out to be Larry, and a thrilled Jessel listens as Larry tells him that upon his return from the war, Eva was waiting for him. With their romantic difficulties resolved, Eva and Larry continued in show business and enjoyed their success together.