Shortly after the end of World War II, aging New York City radio star Jed Potter [Fred Astaire] tells his audience a story that remains unfinished, a romance shaped by Irving Berlin’s music and a life lived on stages and in clubs.
In 1919, rising dancer Jed falls in love with chorus girl Mary O'Hara [Karolyn Grimes] while working in a show, and he urges her to join him in Charles Dillingham's new Broadway production, arguing it could lift her from the chorus to a lead role. Mary declines the Broadway offer but agrees to let him take her to a nightclub owned by crooner Johnny Adams [Bing Crosby], Jed's former vaudeville partner and Army buddy. The three attend a party that night, where Johnny and Mary dance together and confess their feelings; Mary agrees to take the role in the Dillingham show.
On opening night, Mary tells Jed that she wants to marry Johnny, though Jed warns that his shiftless friend isn't the marrying kind. Later, Mary meets Johnny at his nightclub, which he has just sold while planning to open a new place, and suggests they marry; he tells her he does not want stability, prompting her to end their relationship. For the next two years, Jed helps Mary forget Johnny. During a dress rehearsal, Johnny reappears, and Jed shares his plan to propose to Mary. When Jed proposes, she says she needs more time to think.
Jed takes Mary to Johnny's new nightclub, where Johnny and Mary embrace and eventually marry. The couple moves from city to city as Johnny opens and sells a string of nightclubs. Three years later in New York City, after Mary has given birth to a baby girl named Mary Elizabeth, Johnny resolves to settle down and opens Top Hat, his most successful club. However, some time later, Mary learns that Johnny plans to sell the Top Hat and issues an ultimatum. He sells the club despite her protests, and they divorce.
Years later, Jed and Mary's new show opens in Chicago, where Johnny has recently opened a new club. While Mary is out, Johnny visits Mary Elizabeth, who recognizes him as her father and tells him that Mary will marry Jed the next week. When Jed and Mary visit Johnny's club to invite him to the wedding, Mary is distraught to find that he has left town. Realizing that Mary will always love Johnny, Jed calls off the wedding. Jed becomes drunk before a show in Detroit, and despite Mary's concerns, he goes onstage to perform a dangerous dance on a bridge and accidentally falls, ending his dancing career.
In the present, Jed relates on the radio that Mary blamed herself for his accident, and that he has not seen her since that night. Jed announces that Johnny is in the studio, after touring with the troops during World War II. As Johnny sings
> You Keep Coming Back Like a Song
Mary suddenly arrives and the three embrace, before Jed, Johnny, and Mary leave the studio together.
