In 1945 New York City, on Victory over Japan or V-J Day, veteran Jimmy Doyle attends a show at the New York Theatre that features Tommy Dorsey and his orchestra. There, Jimmy unsuccessfully tries to seduce several women. Although Women’s Army Corps member Francine Evans rejects him, he persists anyway. An acquaintance of Francine’s named Arnold Trench informs her that her friend, Paul Wilson, is also at the show, and when they reunite Paul tells her he will telephone her the next day. Meanwhile, Jimmy’s friend, Eddie Di Muzio, asks for Jimmy's hotel room key because he met a girl. Eddie’s date, Ellen Flannery, turns out to be friends with Francine. Eddie and Ellen leave and Jimmy is left alone with Francine, but she brushes him aside and leaves. Four hours later, Jimmy calls his room, but Eddie has not yet finished his romantic interlude. In the morning, Jimmy finds Francine at the hotel’s front desk looking for Ellen. Jimmy, who has been jumping from hotel-to-hotel and writing bad checks, must make a quick escape to avoid the desk clerk. He asks Francine to get his suitcase and saxophone from the room and they meet outside in a taxicab. Jimmy is late for an audition in Brooklyn and insists Francine go with him. At the audition, the club owner tells Jimmy that he is playing too loud. Francine suggests Jimmy adjust his style and Jimmy becomes angry. While apologizing to Francine, Jimmy argues with the club owner. Francine interrupts by singing and encourages Jimmy to accompany her. The club owner loves the act and hires them as a duet. A romance ensues, but Francine soon learns from her agent, Tony Harwell, that she can return to her job singing with Frankie Harte’s band. Sometime later, Tony delivers a letter from Francine to Jimmy at the club, explaining her absence, and Jimmy asks Tony to represent him. Jimmy travels to Francine’s show in Roanoke, Virginia, and makes a scene. Paul Wilson, the piano player, steps in, and when Francine takes Jimmy outside, he professes his love for her. Francine arranges for Jimmy to audition for bandleader Frankie Harte, and he joins the band. Traveling by bus, the band crisscrosses the southern U.S. and Jimmy and Francine grow closer. When she allows him to read a love poem, Jimmy insists they leave the motel in the middle of the night to go to the justice of the peace. Francine is disappointed in Jimmy’s proposal and says she will not marry him. In response, Jimmy crawls under a taxicab and orders the driver to run him over. He professes his love once more and Francine agrees to the marriage. Later, one of the band members is caught with an underage girl and Frankie bails him out. Tired of losing money, Frankie tells Francine that he is canceling the rest of the tour. However, she suggests he let Jimmy take over the band. Frankie grudgingly agrees and the band lands a gig at a hotel in Chicago, Illinois, now called “Jimmy Doyle and his Orchestra.” The band is a hit and Francine is praised in a newspaper review. During rehearsals, Jimmy clashes with band members and loses his temper when Francine intervenes. She later leaves the stage in the middle of a show. Jimmy goes after her, and she announces that she is pregnant and wants to return to New York City. Upset, Jimmy insists she stay with the band, but finally agrees to let her go. Back in New York City, Tony finds Francine doing studio recording work, while Jimmy and the band tour with a new singer, Bernice Bennett. Eventually, Jimmy turns the band over to pianist Paul and returns to New York City three days later than planned. There, he tells Francine that the band did not work out and that he needed some time alone. Jimmy works on a tune and Francine adds lyrics, calling it “New York, New York.” Later, Jimmy tells jazz musician Cecil Powell that his former band members were not good enough, and he wants to play with the best. Cecil invites Jimmy to sit in with his quintet at the Harlem Club. The following day, Jimmy picks up Francine at the recording studio and explains where he was the night before. Francine, now six months pregnant, asks Jimmy to pay more attention to her. Jimmy takes Francine to see their former band, now billed as Bernice Conrad and the Paul Wilson Orchestra. Francine invites her old friend Ellen Flannery and Decca Records producer Artie Kirks, hoping they will hit if off. At the show, Jimmy is displeased, becomes intoxicated, and confronts Paul onstage. After being forcibly removed from the club, Jimmy plays his saxophone beside a billboard for Paradise Park. The next day, he picks up Francine from the studio with a car full of flowers and they make up. Francine brings Tony and Artie to the Harlem Club to discuss a recording deal that Artie recently offered her. Francine is concerned about the baby and Artie and Tony promise to get her a nurse for the road. Jimmy claims he approves, but leaves to make a telephone call. After Artie and Tony leave, Francine drinks and makes her way toward the stage. Jimmy notices, and starts wailing on his saxophone. Francine dances with a man and appears to leave with him. Jimmy rushes out, sees the man get in a taxicab, and follows it in his car. Francine, who is actually sitting in the back seat of Jimmy’s car, covers his eyes with her hands and the car runs up on the curb. Jimmy drives recklessly as they argue over the baby and the fights turns physical. Francine begins screaming in pain and Jimmy drives her to a hospital. Francine gives birth, and when she informs Jimmy that she named the child after him, he becomes angry. Jimmy claims he does not want to see the child because he does not plan to stay and raise him. Francine says she loves him, but Jimmy says that is not possible, and says goodbye. Several years later, Francine records a song as Artie and Paul look on and her son sleeps in the studio. Francine goes to Hollywood, California, to star in a movie musical called Happy Endings. In the movie, Francine’s character is an usherette named “Peggy Smith,” who imagines she is a Broadway star. Later, Jimmy watches the movie in a theater. Meanwhile, a radio disk jockey begins using Jimmy’s instrumental, “New York, New York,” as his theme and it becomes a hit on the jazz record charts. Jimmy goes to the Starlight Terrace to see Francine perform and she notices him in the audience. She then performs “New York, New York,” with her lyrics. Jimmy visits Francine in her dressing room amid a crowded after-party, but he is uncomfortable. On his way out, Jimmy says hello to Jimmy, Jr. Jimmy calls Francine from a phone booth outside the stage door and invites her to join him for Chinese food because there is something he wants to discuss. She agrees, but has second thoughts and leaves him waiting.