Set during the Napoleonic Wars, "The Firefly" follows Nina Maria Azara, a beautiful and alluring Spanish singer who is also a spy. Her mission is to seduce French officers in order to uncover Napoleon's plans for Spain. She is sent to Bayonne, France, to gather military secrets. Before her mission, Nina performs at a club where she meets Don Diego, unaware that he is actually Captain Andre, a French spy sent to observe her. While in France, Nina falls in love with Don Diego before discovering his true identity. Despite heartbreak and danger, Nina manages to outwit her pursuers and returns to Spain, only to be captured when Napoleon's troops invade. In an unexpected twist, Nina and Captain Andre are reunited, but their homelands are now at war. Cast: - Jeanette MacDonald as Nina Maria Azara - Allan Jones as Don Diego / Captain Andre - Warren William as Colonel de Rouchemont - Billy Gilbert as Inn Keeper - Douglass Dumbrille as Marquis de Melito - Henry Daniell as General Savary - Leonard Penn as Etienne DuBois - Tom Rutherford as King Ferdinand - Belle Mitchell as Lola - George Zucco as St. Clair, Secret Service Chief - Corbet Morris as Duvall - Matthew Boulton as Duke of Wellington Runtime: 131 minutes.