A hidden monastery in northern Spain guards a secret: its walls house the Order of the Knights of Heliopolis, a brotherhood of immortal alchemists who pursue their studies in secrecy. In the late eighteenth century, the student Siebzehn undergoes a life-and-death trial there to be accepted into the ranks of the knights. However, when his master reveals the secret of his origins to the other brothers of the order, Siebzehn is faced with a grave decision. For he is the legitimate son of Louis XVI and Marie Antoinette: King Louis XVII of France. Will he choose the life of a Knight of Heliopolis or attempt to claim his heritage as a ruler? The fate of Louis XVII, who allegedly died in prison at just ten years old, is one of the great myths of France. With "The Knights of Heliopolis," Alexandro connects these threads.