At first glance, the street singer and florist Sonja could be taken for Eliza Doolittle's cousin. But while she unwittingly becomes part of a linguistic experiment conducted by two elderly friends and blossoms into a fair lady, the protagonist of the operetta, composed by Leo Fall in 1922 to a cheerful libretto by Lo Portem and August Neidhart, she deliberately allows herself to be used as the subject of a bet. American millionaire Brown wants to marry his daughter Mabel to inventor Mr George for financial reasons, but she has her eye on George's secretary and will only comply if her official fiance can turn any street girl into an 'interesting woman' within three weeks. Exquisite, inventive music accompanies the cheerful events peppered with local dialects, whose tongue-in-cheek ending turns the tables on the original bet