New York, New York

In September 1945, the film opens with Jimmy Doyle celebrating V-J Day at the Rainbow Room, marking the end of World War II. Ex-soldiers like Jimmy join the festivities, highlighting the joyful atmosphere of victory. Jimmy's attempt to pick up women showcases his carefree post-war attitude.

Jimmy notices Francine Evans, a singer, sitting alone at the celebration. He makes a persistent romantic advance, despite her annoyance at his refusal to take no for an answer. Their initial encounter sets up the romantic tension between the two characters.

The next morning, Jimmy is found being evicted from his hotel for unpaid bills. Coincidentally, Francine's friend Ellen, who was borrowed for the night, is involved in the aftermath. Jimmy then jumps into Francine's taxi, insisting she accompany him to the Palm Club.

Jimmy attempts to audition as a tenor saxophonist at the Palm Club. Francine sings along to his music, impressing the owner, who then offers both Jimmy and Francine jobs at the club. This marks the beginning of their professional collaboration and romance.

Francine is offered a new job as the lead singer of Frankie Harte's band, and she departs for a tour, leaving Jimmy heartbroken. He shows up at her hotel, expressing his love and trying to convince her to stay, but she is committed to her new opportunity.

Jimmy leaves his solo gig to join Frankie Harte's band in hopes of staying close to Francine. However, he becomes frustrated by Harte's refusal to let him perform his own, more modern music, leading to tension in his professional life.

Jimmy, touched by Francine's poetry about him, drags her to marry him in a spontaneous wedding after she is annoyed by his lack of proposal. Their union shows their deepening emotional connection despite the chaos in their careers.

In early 1946, Jimmy takes over the band after Frankie Harte retires, but faces difficulties booking gigs. Francine becomes pregnant and plans to have the baby in New York, causing tension as Jimmy feels overwhelmed and frustrated by their changing lives.

Jimmy hires a lesser singer, Bernice Bennett, with whom he briefly has an affair. He leaves to find Francine, and they reunite, but their relationship is strained by his new nights at the Harlem Club and their ongoing disagreements.

Columbia producer Artie Kirks offers Francine a recording opportunity, stirring Jimmy's jealousy. An intense argument ensues, climaxing with them fighting in the car and Francine going into labor, which makes Jimmy realize the seriousness of their situation.

Franecine gives birth to their son, Jimmy Jr., at the hospital after a heated argument. Both are overwhelmed with emotion, reaffirming their love for each other amidst the chaos of their personal life.

Several years later, Francine becomes a successful stage, screen, and recording star. Jimmy owns a nightclub named the Major Chord, and his famous instrumental 'New York, New York' becomes a hit, symbolizing his success and their ongoing intertwined lives.

Jimmy sees Francine perform and meets her backstage, where their young son is present. They share a moment of connection, but ultimately she chooses to return to her career and her party, leaving Jimmy alone, reflecting on their complicated relationship.