Calderon spins a metaphysical tale about Segisimund, who is imprisoned by his father, the King, because it is prophesied that Segisimund would become a tyrant. One day the King relents and Segisimund awakens from his nightmare to find himself crown prince. His actions prove the prophesy correct, and he is banished once again, where he convinces himself that everything that has happened to him is but a dream. He subsequently escapes and learns to rule wisely.