In January, 1796, Marie-Therese, the only surviving child of Marie Antoinette and Louis XVI arrived in Vienna in the care of her first cousin, the Holy Roman Emperor Francis II, who had smuggled her out of France after the Reign of Terror. For three years Francis tried to convince Marie-Therese to assert her hereditary rights and allow him to invade the newly vulnerable democracy, but Marie-Therese refused, ultimately fleeing her cousin's Hofburg Palace for Mittau, where her exiled uncle, King Louis XVIII, married her off to his son. At Mittau, Marie-Therese wrote her memoirs, and, upon their publication, immediately became the enduring symbol of the Bourbon Restoration and a figure of fascination around the world. Yet for all of her fame Marie-Therese's later life remains shrouded in mystery. To this day, many believe that the real Marie-Therese, traumatized following her family's sudden execution, was spirited away to Eastern Europe, where she switched identities with a childhood playmate and lived out the rest of her life in seclusion as 'The Dark Countess'. Now, two hundred years later, this theory is finally put to rest. Interweaving extensive details gleaned from an impressive cache of undiscovered Bourbon family letters, and Marie-Therese's previously unpublished journals Nagel tells the remarkable story in full and draws a vivid portrait of an astonishing woman who both defined and shaped an era.