"Impossible, sir."
"Or passed you at the door?"
"No, sir; I never left my post except when I walked my rounds."
"What other openings are there in the museum?"
"There is the door into Mr. Ward Mortimer's private rooms."
"That is locked at night," my friend explained, "and in order to reach it anyone from the street would have to open the outside door as well."
"Your servants?"
"Their quarters are entirely separate."
"Well, well," said the inspector, "this is certainly very obscure. However, there has been no harm done, according to Mr. Purvis."
"I will swear that those stones are genuine."