At first glance, the street singer and flower seller Sonja could be mistaken for Eliza Doolittle's cousin. But while she unwittingly gets caught up in the linguistic experiment of two elderly friends and blossoms into a fair lady, the protagonist of the operetta, which Leo Fall composed in 1922 to a cheerful libretto by Lo Portem and August Neidhart, deliberately allows herself to be used as the object of a wager: The American millionaire Brown wants to marry off his daughter Mabel to the inventor Mr. George for financial reasons; however, she has her eye on George's secretary and will only comply if her official fiancé can transform any streetwalker into an "interesting woman" within three weeks. Delightful, 'catchy' music accompanies the lively goings-on, peppered with popular sayings, whose tongue-in-cheek happy ending reverses the omens of the original bet.