On a visit to a spa in the Ruritanian Kingdom of Tyronia, American financier Richard Gresham meets the country's ruler, King Anatol XII, and convinces him that he could arrange for $50 million dollars in loans to benefit his impoverished nation if the king's charming daughter could do reciprocal public relations in the States. Unfortunately Princess Catterina falls ill with the mumps and is quarantined for a month aboard ship. Rather than risk having his very lucrative endorsement deal fall through, Gresham hires out-of-work lookalike actress Nancy Lane to impersonate Catterina. Complications arise when she falls in love with investigative reporter Porter Madison, who is looking into Nancy Lane's disappearance. She tries to maintain the precariously delicate balance of playing the two parts convincingly with both the loan and her heart at stake.
