There are all sorts of legends concerning lost or displaced royalty, but I find this one to be particularly interesting. The legend of the Dark Counts revolves around speculation about a couple who had moved into a castle in Eishausen in the German state of Thuringia in1807. The Count identified himself as Count Vavel de Versay but never divulged the woman’s identity, though he made it quite clear that he was only at her side as a protector and caregiver.  The woman herself hardly ever left the castle, and when she would leave, she would always be in her carriage and wearing a dark, heavy veil to conceal her face. 
The Count’s real name was Leonardus Cornelius Van der Valck, and it’s known that he was a secretary in the Dutch embassy in the late 1790s. When the Countess died in 1837, he gave her name as Sophia Botta, and she was buried very quickly with little ceremony. The Count died in 1845, and the secret of the Countess’s true identity went to the grave with him. 
One very popular theory that existed was that the Countess was in reality Madame Royale, or Princess Marie-Therese-Charlotte, the oldest daughter of Louis XVI and Marie Antoinette and the sole member of the royal family to have survived the Revolution. Marie Therese was held in the temple until 1795 when she was conveyed to Austria during a prisoner exchange. She married her cousin, the Duc d’Angouleme, and died childless in 1851. The story goes that the real Marie Therese, traumatized by what she had suffered during the Revolution and left pregnant from a rape, switched places with her half-sister Ernestine de Lambriquet and went on to live a quiet life as the Countess while Ernestine masqueraded as Madame Royale. What were the reasons behind this? Marie Therese bore little to no resemblance to the portraits painted of her as a child, and her mannerisms were quite different. 
And who was Ernestine de Lambriquet? Ernestine was, supposedly, the daughter of Louis XVI and a married serving maid. The story, retold by Susan Nagel in her biography of Madame Royale, is as follows:
The substitution theory, which keeps flaring up like wild fire on internet discussion forums, claims that Louis XVI had an “operation” and was encouraged by his wicked brother Provence to test his prowess upon a serving maid. The maid, who was a married woman, gave birth to a daughter named Marie-Philippine Lambriquet. Marie-Antoinette eventually adopted the girl and renamed her “Ernestine” after a character in one of her favorite novels. Ernestine and Madame Royale were educated together. 
According to Antonia Fraser’s biography of Marie Antoinette, Marie Antoinette: The Journey, the young Dauphin and Dauphine were unable to consummate their marriage for years due to a deformity of Louis XVI’s penis. It took the intervention of Marie Antoinette’s older brother Emperor Joseph II for Louis to undergo surgery so that he would be able to consummate the marriage. This coincides with the “operation,” and it was well-known that while Louis hadn’t inherited Louis XIV’s and Louis XV’s voracious appetite for women, his brothers had. Also, Marie Antoinette had adopted two other children into the royal household, so it wasn’t exactly an unusual thing for her to do.  But the problem is that Louis had no maitresse en titre, unlike the two previous kings whose name he bore, and that he was sincerely devoted to his wife and family and to his own pursuits. In addition, records also show that Ernestine de Lambriquet remained in France in 1795, married in 1810, and died in 1813. 
Still, there is testimony that while the putative Madame Royale may not have been Ernestine de Lambriquet, it may have been someone else, and that the Countess was still Madame Royale. There were rumors that the Dark Countess wore a veil because of fear of being recognized by her resemblance to both of her parents, and that there were patterns of lilies on her clothing and jewelry, which could be taken as Bourbon lilies and mark her as a member of the House of Bourbon. 
So what do I think? I think the story is a bunch of bunk. The first reason is Louis XVI’s love for his The first reason is Louis XVI’s love for his wife and family, and the fact that there were no scurrilous rumors of affairs with other women before and during the course of his marriage to Marie Antoinette. And as for the change in Marie Therese’s mannerisms? Let’s not forget that she and her family were moved into the Temple in 1792, and that she wasn’t released until 1795. In between those years, she lost both her parents, her aunt, and her younger brother, and she didn’t know what had happened to any of them until close to her release from prison. Trauma and rapid change like that are hard for any person, especially a for young girl who’s accustomed to a certain lifestyle and who has spent a lot of her life sheltered from the big, cruel world. If she had been raped or sexually abused during her time in prison, that just adds more to the reason why her mannerisms and personality may have changed, because it’s more to process and deal with. But to be honest, I think that Robespierre and later the Directory would have done what they could to keep Marie Therese safe from that kind of harm. Salic law prevented women from inheriting the French throne, but Marie Therese was still an important bargaining chip because France was at war on and off with Austria. Paul Barras and Charles Talleyrand, who were both key figures in the Directory government, would have known this, and being the shrewd, calculating men they were, they would have done what they could to make sure that Marie Therese remained marriageable.
The identity of the Countess herself is as much of a mystery to me as it has been to everyone else. Perhaps she was simply a wealthy woman who had some strange photosensitivity or who may have been scarred from a bout with smallpox, and who may have wished to live the rest of her life in relative peace and quiet. Were she an émigré aristocrat who had fled France after the Revolution had started, she would no doubt have done what she could to live out the rest of her life in relative comfort and stability. Whoever she was, she certainly seemed to have had that at the end of her life.
As a side note, the Count and Countess are interred in a cemetery in Eishausen. Though there has been talk of doing so, no attempt has been made to exhume the Countess’s body for DNA testing. 
“Dunkelgrafen.” Wikipedia. <www.wikipedia.org>
“The Theory of Substitution and Madame Royale.” Madame Royale. <www.madameroyale.de>
Vidal, Elena Maria. “Madame Royale and the Subsitution Theory.” Tea at Trianon.<www.teaattrianon.blogspot.com>