Radio broadcaster Jed Potter opens his radio program by telling his audience about three performers who were influenced by Irving Berlin's music: In 1919, when the song "A Pretty Girl Is Like a Melody" is a hit, Jed is in love with pretty chorus girl Mary O'Hara. However, Mary falls in love with Jed's former vaudeville partner, crooner and shiftless nightclub owner Johnny Adams. Jed helps Mary get a starring role in a big Broadway production, while Johnny opens and sells a series of clubs. Johnny and Mary quickly fall in love, and on her opening night, she suggests they marry, but he turns her down, insisting he does not want stability. Two years pass, and Jed gallantly helps Mary forget Johnny and eventually proposes, but Johnny reappears, and he and Mary wed. The couple moves from town to town as Johnny opens nightclub after nightclub, and in New York, three years later, after Mary has given birth to a baby girl named Mary Elizabeth, Johnny opens the Top Hat, his most successful club. When Mary learns that Johnny plans to sell it, she issues an ultimatum, but he sells the club despite her protests. Mary and Johnny divorce, and years later, Mary and Jed's show opens in Chicago, where Johnny has just opened a new club. Johnny visits Mary Elizabeth, who realizes that he is her daddy and has him sing her a song about "running around in circles." She also tells Johnny that her mother will be marrying Jed the next week, and Johnny skips town. When Mary and Jed visit Johnny's club to invite him to the wedding, Mary is distraught to find him gone, and Jed realizes she will always love Johnny and calls off the wedding. Despite Mary's admonition, Jed drinks before going onstage to do a dangerous dance on a bridge and falls, ending his dancing career. Jed now relates over the airwaves that Mary blamed herself for his injury, and Jed has not seen her since that night. Jed makes a public appeal during the broadcast for Mary to return to Johnny, who, after touring with the troops during World War II, is in the studio. As Johnny sings, Mary joins him and they embrace. Jed, Johnny and Mary then leave the studio together.
