St. Leon is the story of a French aristocrat, Count Reginald de St. Leon, who loses his fortune gambling and experiences guilt that almost drives him crazy. Count Reginald narrates his life story, starting with his father's death when he was an infant. He was brought up by his mother, a woman full of the prejudices of aristocracy and magnificence. Reginald had great regard for aristocratic honor. After being inspired by his uncle, the Marquis de Villeroy, he joined the Italian war of 1521–1526, hoping to gain military fame in the battle of Pavia. When he returned home from service, he found out that his mother was dead, and the twenty-year-old was forced to take control of his own affairs. The novel explores the themes of immortality, love and friendship, integrity, and religion. Godwin combines elements of domestic, philosophical, and fantasy novels into a historical fiction of extensive range. There are exciting gothic elements in the story.