Historian Wilkinson (Louis XIV: The Power and the Glory) illuminates the political upheavals of 17th-century France in this meticulous look at the case of Eustache Dauger, the prisoner believed to be the Man in the Iron Mask. She documents harsh conditions at the prisons where Dauger was held, and fills in gaps in the historical record by profiling his fellow inmates, including Count Nicolas Foucquet, whose sentence was changed by Louis XIV from “perpetual banishment” to “perpetual imprisonment,” and the Comte de Lauzun, who was arrested after interfering in his cousin’s affair with the king.