The Firefly (1937 film)

The Firefly is a 1937 musical film starring Jeanette MacDonald and Allan Jones. The film is an adaptation of the operetta of the same name by composer Rudolf Friml and librettist Otto A. Harbach that premiered on Broadway in 1912. The film used nearly all of the music from the operetta but jettisoned the plot in favor of a new storyline set in Spain during the time of the Emperor Napoleon I. It added a new song, "The Donkey Serenade" (a reworking by Herbert Stothart of Friml's 1918 orchestral piece 'Chanson'), which became extremely popular, as was one of the Friml songs, "Giannina Mia". The original release prints of the film were elaborately tinted with Sepia-Blue, Sepia-Orange and Sepia-Blue-Pink.
Plot.
Secret agent Nina Maria Azara (Jeanette MacDonald) is working undercover for the King of Spain (Tom Rutherford) as a singer known as the "Mosca del Fuego" or "Firefly." Despite her love for Captain Andre (Allan Jones), she tricks him so that his general will change the French defensive positions, thus allowing the Duke of Wellington to win the Battle of Vitoria. In the end Nina and Andre leave together for a new life in peace.