In 1912, 52nd Street is populated by members of the highest social circles, including Rufus Rondell and his spinster sisters, haughty Adela and timid Letitia. Adela is outraged when Rufus marries beautiful cabaret singer Evelyn Macy, and although Letitia defends them, Adela refuses to sanction their love and disowns Rufus. While the newlyweds tour Europe, Evelyn's friends, Sid and Jack, open their own nightclub and hire Fiorello Zamarelli, an immigrant accordian player who dreams that his son Benjamin will be a concert pianist. In 1915, Sid and Jack receive a letter from Rufus saying that Evelyn is ill after the birth of their daughter Margaret. Rufus brings his family to the house across the street from Adela's, which he inherited from his father, but it is too late to restore Evelyn's health. Before she dies, Evelyn begs Rufus to rear Margaret to be a lady, proper enough to fit into her aunts' social circle. As the years pass, Margaret is educated at the finest boarding schools, while 52nd Street is gradually taken over by speakeasies. Soon the only stately homes left are Rufus' and Adela's, but Rufus is forced to turn his home into a club to avoid bankruptcy, and he becomes partners with Fiorello, who is horrified when he discovers that Benjamin is a musician in Sid and Jack's club. In 1929, many people are ruined by the stockmarket crash, but Rufus, Fiorello, Sid and Jack all prosper. Rufus discreetly supports his sisters, who do not know that they lost their money. Adela's vengeance continues, and now takes the form of influencing her friends to turn down invitations to a party for Margaret. Fiorello overhears Rufus discussing the matter and he goes to Adela and Letitia in an attempt to heal the breach. Adela refuses to give in, but Fiorello is touched by Letitia's scrapbook of Margaret's life. Sid, Jack and Benjamin decide to throw Margaret a perfect party and coach their fellow entertainers on how to act like society swells. Their plans fall through, however, when Margaret, who does not know what Rufus' business is, insists on proving to Rufus that she is not a snob. Benjamin starts a commotion at the party to please her, and soon everyone is arrested. Later, Margaret tells Rufus she wants no part of her aunts' life and prefers to be a performer like her mother. Despite Rufus' adamant objections to her plans, as well as her romance with Benjamin, Margaret gets a job singing at Sid and Jack's. Fiorello is again determined to play peacemaker, and he, Benjamin and Margaret go to see Adela and Letitia. Overjoyed finally to see Margaret, Adela agrees to reunite the family, especially when she learns that Rufus has been supporting her. The sisters open a nightclub in their home and are soon doing booming business. One night, Letitia fulfills her lifelong desire to perform, and while she is singing Rufus comes in. He is furious and about to leave when Margaret enters, singing Evelyn's song. Rufus is won over and the reunited Rondell family wholeheartedly approves of Benjamin and Margaret's love.