The Firefly

As Napoleon plots to take over Spain, Nina Maria Azara (Jeanette MacDonald), a beautiful singer, travels to Bayonne as an undercover spy accompanied by Don Diego (Allan Jones), a French spy she believes to be a Spanish nobleman. The two fall in love. When her attempts to relay information to the Spanish about France's plan to force King Ferdinand VII to step down are sabotaged, she realizes Diego is a spy and flees. Five years later, with France and Spain at war, the two are reunited.