In the Roman Coliseum, at the beginning of the Christian era, the Emperor Turnerius, accompanied by his favorite, Nerissa, watches the bestial games in the arena. His son Gordian is asked by Grimaldo the magician to save the life of a Christian girl about to be thrown to the lions. He refuses, whereupon Grimaldo prophesies the fate of the Empire by telling the prince a story of the future: Two thousand years hence, in New York, a parallel situation takes place in which a young man is led to put a stop to the base plans of his father. The prince is so deeply affected by the injustice of the story that he plunges into the arena to save the girl, causing the emperor to die in a fit of rage, thus precipitating the coronation of his son as the new emperor.