神探John Kent (Randolph Scott), a former star football player at Harvard, goes to Paris with his friend Huck Haines (Fred Astaire) and the latter's dance band, the Wabash Indianians. Alexander Voyda (Luis Alberni) has booked the band, but refuses to let them play when he finds the musicians are not the Indians he expected, but merely from Indiana (Huck Haines and his Indianians Band).John turns to the only person he knows in Paris for help, his Aunt Minnie (Helen Westley), who owns the fashionable "Roberta" gown shop. While there, he meets her chief assistant (and secretly the head designer), Stephanie (Irene Dunne). John is quickly smitten with her.Meanwhile, Huck unexpectedly stumbles upon someone he knows very well. "Countess Scharwenka", a temperamental customer at Roberta's, turns out to be his hometown sweetheart Lizzie Gatz (Ginger Rogers). She gets Huck's band an engagement at the nightclub where she is a featured entertainer.Two things trouble John. One is Ladislaw (Victor Varconi), the handsome Russian deposed prince and doorman who seems too interested in Stephanie. The other is the memory of Sophie (Claire Dodd), the snobbish, conceited girlfriend he left behind after a quarrel over his lack of sophistication and polish.When Aunt Minnie dies unexpectedly without leaving a will, John inherits the shop. Knowing nothing about women's fashion and that his aunt intended for Stephanie to inherit the business, he persuades Stephanie to remain as his partner. Correspondents flock to hear what a football player has to say about feminine fashions. Huck gives the answers, making a lot of weird statements about the innovations John is planning to introduce.Sophie arrives in Paris, attracted by John's good fortune. She enters the shop, looking for a dress, but is dissatisfied with everything Stephanie shows her. Huck persuades her to choose a gown that John had ordered discarded as too vulgar. When John sees her in it, they quarrel for the final time.John reproaches Stephanie for selling Sophie the gown. Terribly hurt, Stephanie quits the shop. With Roberta's putting on a fashion show in a week, Huck takes over the design work, with predictably bad results. When Stephanie sees his awful creations, she is persuaded to return to save Roberta's reputation.The show is a triumph, helped by the entertaining of Huck, Countess Scharwenka, and the band. (A pre-stardom Lucille Ball, with platinum blond hair, appears uncredited in her first RKO film[4] as a model wearing an elaborate feather cape, after the vocal by Dunne, in the fashion show.[5]) The closing sensation is a gown modeled by Stephanie herself. At the show, John overhears that she and Ladislaw are leaving Paris and mistakenly assumes that they have married. Later, he congratulates her for becoming a princess. When she informs him that Ladislaw is merely her cousin and that the title has been hers since birth, the lovers are reunited. Huck and Lizzie, who decide to get married, do a final tap dance sequel.