The Firefly (1937)

Nina Maria Azara is the beautiful, alluring singing spy for Spain during the Napoleonic Wars. Her mission is to seduce French Officers so they will reveal Napolean's intentions toward Spain. She is sent to Bayonne, France to gather military secrets. Prior to this, she meets Don Diego while performing at a club. Unknown to her, Don Diego is actually Captain Andre, who is sent to Spain to spy on her. While in France, Nina discovers Diego's true identity--after she has fallen in love with him. Nina outwits her potential captors and returns to Spain, and goes into hiding. Napoleon's troops invade Spain, resulting in Nina's capture. In a strange twist of fate, Nina and Captain Andre are reunited, but the two nations are now at war.