On her way to New York to find financial backing for her impoverished country, the Ruritanian romance Kingdom of Taronia, Princess "Zizzi" Catterina (Sylvia Sidney) falls ill with the mumps and has to be quarantined for a month. In desperation, financier Richard Gresham (Edward Arnold (actor)), who is planning to issue $50 million in Taronian bonds, hires unemployed lookalike actress Nancy Lane (Sidney again) to impersonate the princess, and offers her a large bonus if she changes the mind of the chief opponent of the financial transaction, newspaper publisher Porter Madison III (Cary Grant).