'To know that secret staircase'

Via Tiny-Librarian: 

….I was puzzling over the transparent fact that either of the apparent exits would have led her directly into the hands of the enemy, when the idea of a secret staircase suggested itself. A little judicious inquiry elicited the information that one did exist. “But it is not seen. It is locked. To view it, an order from the Commissary—that is necessary,” explained the old guide.

To know that a secret staircase, and one of such vivid historical importance, was at hand, and not to have seen it would have been too tantalising. The “Commissary” was an unknown quantity, and for a space it seemed as though our desire would be ungratified. Happily the knowledge of our interest awoke a kindly reciprocity in our guide, who, hurrying off, quickly returned with the venerable custodian of the key. A moment later, the unobtrusive panel that concealed the exit flew open at its touch, and the secret staircase, dark, narrow, and hoary with the dust of years, lay before us.

Many must have been the romantic meetings aided by those diminutive steps, but, peering into their shadows, we saw nothing but a vision of Marie Antoinette, half clad in dishevelled wrappings of petticoat and shawl, flying distracted from the vengeance of the furies through the refuge of the low-roofed stairway. 

--A Versailles Christmastide by Mary Stuart Boyd