In an effort to maintain control of Mexico, Napoleon III (Claude Rains) of France installs the puppet leader Emperor Maximilian (Brian Aherne) to execute his commands and to wrest power from Benito Juárez (Paul Muni), Mexico's elected president. Maximilian questions his role, but his power-hungry wife, Empress Carlota (Bette Davis), pushes him to remain emperor. However, the will of the people and the fickleness of Napoleon's support put Maximilian in a precarious position.