For more than 30 years, Eustache Dauger was held in the prison system of Louis XIV's France—never to be freed. In a novel, Alexandre Dumas immortalized the image of masked prisoner in a dungeon, and so it can be easy to forget that this tale is actually true. Spanning decades and four different prisons, Josephine Wilkinson's illustrated history shows what life was really like for state prisoners in 17th-century France, and offers tantalizing insight into why this mysterious man was arrested and why his story would become one of France's most intriguing and controversial legends.