d yet the stones are
all here."

"It is certainly most extraordinary," said the inspector. "I never
remember a case like it. Let us see the watchman."

The commissionaire was called--a soldierly, honest-faced man, who
seemed as concerned as Ward Mortimer at the incident.

"No, sir, I never heard a sound," he answered, in reply to the
questions of the inspector. "I made my rounds four times, as usual,
but I saw nothing suspicious. I've been in my position ten years, but
nothing of the kind has ever occurred before."

"No thief could have come through the windows?"

"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."

"So that the case appears to be merely one of malicious damage. But
none the less, I should be very glad to go carefully round the
premises, and to see if we can find any trace to show us who your
visitor may have been."

His investigation, which lasted all the morning, was careful and
intelligent, but it led in the end to nothing. He pointed out to us
that there were two possible entrances to the museum which we had not
considered. The one was from the cellars by a trap-door opening in the
passage. The other through a skylight from the lumber-room,
overlooking that very chamber to which the intruder had penetrated. As
neither the cellar nor the lumber-room could be entered unless the
thief was already within the locked doors, the matter was not of any
practical importance, and the dust of cellar and attic assured us that
no one had used either one or the other. Finally, we ended as we
began, without the slightest clue as to how, why, or by whom the
setting of these four jewels had been tampered with.

There remained one course for Mortimer to take, and he took it. Leaving
the police to continue their fruitless researches, he asked me to
accompany him that afternoon in a visit to Professor Andreas. He took
with him the two letters, and