Song-filled look behind the scenes of vaudeville, based on the lives of Nora Bayes and Jack Norworth.

In 1905, songwriter and performer Jack Norworth is taken by his magician friend, the Great Georgetti, to see a singer named Nora Bayes, who is performing at a local honky-tonk cabaret run by Dan Costello. In between numbers, Costello encourages Nora to entertain the cabaret's owner, Tim Donovan. Jack is so impressed with Nora's rendition of one of his songs that he offers to help her break into vaudeville. When Costello interrupts their conversation to insist that Nora return to Donovan's table, a fight ensues, and Jack, Georgetti and Nora are thrown out of the cabaret. Jack walks Nora home and promises to get her a tryout at the Crystal Theater where he works. Later, Costello offers to rehire Nora and also proposes marriage, but Nora angrily sends him away. In retaliation, Costello hires a group of ruffians to disrupt Nora's audition. Jack then suggests that Nora and another singer, Blanche Mallory, perform as a sister act at a theater run by his friend, Poppa Karl. Later, believing that Jack favors Nora over her, Blanche quits the act. Jack then marries Nora, and they become a team. They travel around the country singing Jack's songs and are a big success. Later they return to New York, hoping to sign a contract to perform there, but Costello and Donovan have bought up the largest chain of theaters and refuse to book them. Costello then proceeds to pressure other theater owners into blacklisting the couple, and Jack and Nora fall on hard times. Jack writes "Shine On, Harvest Moon," which he is sure will be a hit. His publisher agrees, but wants Blanche, who is now working for Costello, to introduce the song. Blanche will agree only if Jack teams up with her, and when he declines, she refuses to sing the song. One night, Georgetti and his assistant, Margie, visit Jack and Nora, and Margie accidentally discloses Blanche's offer. Not wanting to stand in the way of Jack's success, Nora tells Blanche that she is leaving Jack. Later, Poppa Karl finds Nora working in an Atlantic City music store and tells her that Jack is so depressed by her leaving that he has been fired from every job he has taken. Happily, Nora returns to New York for Jack's opening in burlesque. When Jack sees Nora, he begins to sing to her, and she joins him in a duet. They are seen by a man who works for showman Florenz Ziegfeld, who puts them in the revue. Together they sing "Shine On, Harvest Moon" and are a huge success.