At the Vandeveers' Fifth Avenue mansion, a reception is taking place. The honoree is the Duke of Branford, an English bachelor, the apple of everyone's eyes – especially the social-climbing mothers and their debutante daughters at the party. Annabelle, the Vandeveers' daughter, rebels at her social upbringing. She rejects a proposal from Jack Bartlett, a young dilettante millionaire. To prove his worthiness, Jack promises Annabelle that he will get a real job as a common laborer. He persuades Silas Pompton to hire him in his Consolidated Glass Works. Pompton and his wife meanwhile are in pursuit of the Duke for marriage to their daughter, Geraldine. Through a misunderstanding, the Duke is romantically involved with Annabelle. Bartlett and Geraldine, hurt and angry, on impulse announce their own engagement. In the midst of all of the romantic entanglements, word arrives that Vandeveer's investments in the Cuban-American Iron Mining Company have been lost, wiping out all of Vandeveer's money. Unknown to anyone, the financial collapse was engineered by Pompton. Annabelle, in an attempt to help her father convinces Pompton to hire her at his glassworks. Both she and Jack are to report the following morning.

Act II

Two weeks later at the Consolidated Glass Works, Annabelle and Jack are at work. Jack has made great strides in winning-over his beloved by starting at the very bottom and working his way up. She is, however, still engaged to the Duke and Jack to Geraldine. Bartlett's idea is to improve working conditions at the factory. This has made him very popular with the other laborers. Pompton fires Jack and Annabelle as troublemakers and the workers revolt. They are about to riot and bring harm on Pompton when Vandeveer enters with news that war has been declared against Spain and volunteers are needed. Everyone immediately and enthusiastically joins the movement to fight in Cuba.

Act III

Several weeks later near Santiago, Cuba, the factory workers are now soldiers, the women are in the Nurses Corps. Bartlett is the officer in charge and Annabelle leads the force of Red Cross nurses. Bartlett leads a victorious charge on Santiago and the troops return as heroes. Jack also uncovers Pompton's financial skullduggery and outsmarts him on Wall Street. The Vandeveers' wealth is restored and all the romances get untangled and are resolved to everyone's satisfaction.