A prisoner dies in the Bastille in 1703 after 34 years of captivity, his face always hidden, his identity erased. Rumors swirled that he was a disgraced royal or the king's twin. The archives reveal a stranger truth: a document classifying him as only a valet.

This episode separates the Hollywood myth from the bizarre human reality of the Man in the Iron Mask. It is the story of how an ambitious middle-management jailer's vanity accidentally spawned a 300-year mystery, and how shredded archives were painstakingly reassembled to solve it.

• Why the mask was black velvet, worn only in transit, not iron worn day and night as Voltaire claimed
• How jailer Saint-Mars used an aristocratic-style mask as a prop to make a commoner look like guarded royalty
• The 1669 orders for prisoner Eustache Dauger, treated as top secret yet ...