A young man loves a woman and is not loved in return. What is more, he has a rival. In a costumed cavalcade, the rival causes the young man's horse to slip, and the young man falls, faints, and, when he comes to, is the victim of the delusion that he is the person whose costume he is wearing: the German Emperor Henry IV. His sister converts a villa into a replica of this Emperor's palace so that the young man can live on as Henry IV undisturbed. After twelve years, however, the delusion wears off. Our man, no longer so young, decides not to let anyone know it and to stay on as Emperor, though sane.

After eight more years, his sister dies. But she had visited him shortly before her death and gained the impression that he might now be curable. She tells her nephew this, and soon after her death he brings a psychiatrist to the villa to see what can be done.