The film tells the story of a petty thief Emmanuele Bardone (played by Vittorio De Sica) who is hired by the Third Reich to impersonate an Italian resistance leader, General della Rovere, and infiltrate a group of resistance prisoners in a Milan prison. Gradually, Bardone loses himself in his role and not merely pretends to be a hero of the resistance but actually becomes one, first encouraging his fellow prisoners to show courage and eventually accepting death by firing squad rather than betraying another imprisoned resistance leader.