Princess Marie-Thérèse of France was born the only legitimate daughter of King Louis XVI and Queen Marie Antoinette. Together with her parents and her brother Louis XVII, she was imprisoned by the republicans in the Temple. Her illegitimate half-sister Ernestine wasn't imprisoned with them, though, and added another unsolvable puzzle to the French Revolution.
In 1791, the French Royal Family was imprisoned in the Temple after their flight from the murderous mob (called republican government) had been intercepted at Varennes. The Royal Family means King Louis XVI, Queen Marie Antoinette, the Dauphin Louis XVII, Madame Royale the Princess Marie-Thérèse, and Ernestine. While King, Queen, Prince, and Princess were imprisoned in the Temple, Ernestine was allowed to return to her Royal apartment in the Louvre.
Ernestine was born as Marie Philippine Lambriquet in 1778. The death records at Versailles show the burial of Marie Philippine Lambriquet for the same year. Ernestine’s birth was registered in the ‘Registry of France’, a registry reserved for the offspring of the king. When her mother died in 1788, Marie Antoinette adopted her into the Royal Family despite her titular father being still alive; tellingly, her brother Augustin Louis was not adopted at the same time. Marie Antoinette changed the name from Marie Philippine to Ernestine, if in remembrance of a relative of her own or because the adoption was done on the day of Saint Ernestine is unknown.
From that day, Ernestine received a Royal pension equal to that of Madame Royale; she moved into the apartment near to that of Princess Marie-Thérèse’s, too, and received the same education as the Princess. Charity? Not really. Even as an illegitimate offspring of Louis XVI she would be a useful marriage candidate in a future alliance. Blood does run thicker than bourgeois delicacy.
In June 1791, Ernestine packed her bags and was fetched from the Louvre by her titular father Jacques Lambriquet. She dropped her name Ernestine and became plain Marie Philippine again. Jacques Lambriquet would pay for that act of kindness to his daughter with his life. Accused of abetting and aiding a member of the Royal Family he would walk to the guillotine in 1794. He was basically accused of acting like a father should towards his daughter. Proud man, despicable mob.
In 1793, the King and Queen both took their walks to the guillotine in front of the great unwashed. Louis XVII had been put into solitary confinement in 1793 when it emerged that the Royal Family in exile had proclaimed him King of France and Navarra upon the murder of his father. After the murder of Marie Antoinette, Madame Royal was also held in virtual solitary confinement.
When the death of Louis XVII was announced in 1795, there would have been two sisters who could have identified the dead body; both were kept scrupulously apart from the body and the funeral. Princess Marie-Thérèse was conveyed to Basel at the end of 1795; she was handed over to representatives of the Imperial court of the Holy Roman Empire at Vienna in exchange for French prisoners of war. None of the Austrian representatives or Habsburg relatives had seen Marie-Thérèse for years on end since she had been a very small girl. Had Ernestine been sent instead? Had the Princess gone mad with grief, had she descended into melancholy and depression as some claim? Had she been assigned into permanent care because of her illness?
When the Princess arrived in Vienna, she was told to start dressing in mourning for her brother as that would be expected of her. But why should she when no one in the French Royal Family did so? And they would have been dressed in mourning if Louis XVII had been dead. The realities of the French Royals and the Austrian Imperials were miles apart.
Meanwhile in Paris, Marie-Philippine was still a minor at the murder of her titular father in 1794. But in 1796, she was emancipated (while her brother was not). The act of emancipation did allow her to get her own passport. What did she need that for?
In 1807, a mysterious couple arrived in the German town of Hildburghausen. They were assigned various houses to live in by local authorities until they were moved into Castle Eishausen in 1810. The man was known as Vavel de Versay, in reality a Dutch diplomat called Leonardus Cornelius van der Valck. The woman had no name. She walked in the streets and parks deeply veiled every day and never talked to anyone. She became known to townsfolk as the Dunkelgräfin, the dark countess.
The dark countess died in 1837 and was buried in the local cemetery in a grave bearing no name. Her companion died in 1845 and was buried in the same cemetery. His grave doesn't bear any name either but the inscription of Dunkelgraf, dark count. The opening of the graves of the two strangers has been summarily blocked by local authorities since 1891. The town council has relented on its position in 2012 and exhumations and DNA probes are planned for the near future.
In 1810, the registry of Paris shows the marriage of a Marie Philippine Lambriquet to a Jean Charles Germain Prempain who owned a house near the Louvre; he was a widower with three little children at the time of the marriage. The death of Madame Marie Philippine Prempain was recorded in 1813.
Princess Marie-Thérèse stayed in Vienna until 1799 when she married her cousin Louis Antoine de Bourbon, Duc d’Angoulême. She went into that marriage against the express wishes of her cousin and host Emperor Francis II. She chose a roving life of moving from European court to court as an exile over a ‘safe’ Habsburg marriage.
The Duc d’Angoulême went on to become Admiral of the French Fleet in the restoration of the Bourbon King Louis XVIII; upon the death of Charles X he would have become King of France, if Louis-Philippe of Orléans hadn't usurped the crown in 1830. The Princess meanwhile was involved in a legal battle with the German Karl Wilhelm Naundorff over inheritance rights of her brother Louis XVII; Naundorff is buried in Delft as Louis XVII and his descendants carry the name de Bourbon with approval of the Dutch authorities of the time. Marie-Thérèse died in 1851 at Castle Frohsdorf; her grave is situated in the Franciscan monastery of Kostanjevica near Nova Gorica on the Slovenian Italian border.
It seems that to be really important you need to be buried in at least two different spots at the same time; Louis XVII is buried in Delft and in Paris; Marie-Thérèse in Nova Gorica and Hildburghausen; and Marie Philippine in Versailles and Paris while Ernestine disappeared in a puff of smoke.