is what happened to Louis XIIIV's son. He was imprisoned in the old palace-turned-jail known as the Temple, and died there -- or did he? There are some interesting peculiarities about the imprisonment of the heir to the Bourbon throne -- for a time, he was held incommunicado from his family members; after that, his appearance seemes to have changed, judging from artists' rendering of the boy. Some say the child was switched with another. Upon his death, a physician managed to preserve his heart, and it has been verified through DNA testing to contain mitochondrial DNA from Marie Antoinette's family -- however, reputable (i.e. - political) prisoners held at the Temple during the Napoleonic era described an incident where a child's skeleton was discovered buried on the grounds (counter to the "official" story of the Dauphin's demise) in a shallow grave dug in an area under constant guard.

So was the Dauphin switched with another child -- a relative, perhaps? There were many pretenders in the Europe of the 19th century.