A 1789 print by an anonymous artist depicting The Man in the Iron Mask. (Photo: Anonymous/Public Domain)

The legend of the Man in the Iron Mask goes something like this: until his death in 1703, a prisoner was held for over three decades across France, including at the Bastille, all while wearing an iron mask, obscuring his identity. 

The legend has inspired books, movies, and theories, but even after centuries of research and speculation—Voltaire thought the man was an unacknowledged brother of King Louis XIV—the identity of the man or why he wore the mask has never been explained. 

But now an American college professor says he’s cracked the case, identifying the man as Eustache Dauger. Paul Sonnino, author of the new book, The Search for the Man in the Iron Mask, says it wasn’t an iron mask, but a velvet one, and Dauger did not always wear it. Dauger’s identity has previously been known by historians, as has his occupation (he was a valet), but Sonnino says he’s the first to outline why Dauger ended up in prison. 

Sonnino says Dauger was the valet to a cardinal, who had gotten rich in part by stealing money from English royalty. He was arrested around the same time that Louis XIV was trying to convince the English to join France’s side in the Franco-Dutch War, likely to protect the secret of the theft.

“Dauger must have blabbed at the wrong time,” Sonnino says. ”He was informed when arrested that if he revealed his identity to anyone he would immediately be killed.”

So, The Man in the Iron Mask was not Leonardo DiCaprio. He was a valet with a secret, and, in all likelihood, a plan to stay alive.