Man in the Iron Mask

The prison at Pignerol, like the others that Dauger was later held at, was used for men who were considered an embarrassment to the state and usually only had about half-a-dozen prisoners at a time.

Saint-Mars' other prisoners at Pignerol included Count Ercole Antonio Mattioli (or Matthioli), an Italian diplomat who had been kidnapped and jailed for double-crossing the French over the buying of the important fortress town of Casale on the Italian border. There was also Nicolas Fouquet, a former government minister who had been jailed for embezzlement, and the Marquis de Lauzun, who had married the Duchess of Montpensier, a cousin of the King, without the King's consent. Fouquet's cell was above that of Lauzun.

Dauger was not always isolated from the other prisoners. Wealthy and important ones usually had man-servants: Fouquet for instance was served by a man called La Riviere. These servants, however, would become as much prisoners as their masters and it was thus difficult to find men willing to volunteer for such an occupation. Since La Riviere was often ill, Saint-Mars applied for permission for Dauger to act as servant for Fouquet. In 1675 Louvois gave permission for such an arrangement on condition that he was only to serve Fouquet while La Riviere was unavailable and that he was not to meet anyone else: for instance, if Fouquet and Lauzun were to meet, Dauger was not to be present.

The fact that the man in the mask served as a valet is an important one. Fouquet was never expected to be released, thus meeting Dauger was no great matter, but Lauzun was expected to be set free eventually and it would have been important not to have him spread rumours of Dauger's existence. Historians have also argued that 17th-century protocol made it unthinkable that a man of Royal blood would serve as a manservant — thus very much discrediting those suggestions that Dauger was in any way related to the King.

After Fouquet's death in 1680, Saint-Mars discovered a secret hole between Fouquet and Lauzun's cells. He was sure that they had communicated through this hole without supervision by him or his guards and thus that Lauzun must have been made aware of Dauger's existence. Louvois instructed Saint-Mars to move Lauzun to Fouquet's cell and to tell him that Dauger and La Riviere had been released. In fact they were held in another cell in another part of the prison, their presence there being highly secret.