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 it was his intention to openly tax his
predecessor with having written the anonymous warning, and to ask him to
explain the fact that he should have anticipated so exactly that which
had actually occurred. The Professor was living in a small villa in
Upper Norwood, but we were informed by the servant that he was away from
home. Seeing our disappointment, she asked us if we should like to see
Miss Andreas, and showed us into the modest drawing-room. I have mentioned incidentally that the Professor’s daughter was a very
beautiful girl. She was a blonde, tall and graceful, with a skin of that
delicate tint which the French call “mat,” the colour of old ivory or of
the lighter petals of the sulphur rose. I was shocked, however, as she
entered the room to see how much she had changed in the last fortnight. Her young face was haggard and her bright eyes heavy with trouble. “Father has gone to Scotland,” she said. “He seems to be tired, and has
had a good deal to worry him. He only left us yesterday.”

“You look a little tired yourself, Miss Andreas,” said my friend. “I have been so anxious about father.”

“Can you give me his Scotch address?”

“Yes, he is with his brother, the Rev. David Andreas, 1, Arran Villas,
Ardrossan.”

Ward Mortimer made a note of the address, and we left without saying
anything as to the object of our visit. We found ourselves in Belmore
Street in the evening in exactly the same position in which we had been
in the morning. Our only clue was the Professor’s letter, and my friend
had made up his mind to start for Ardrossan next day, and to get to the
bottom of the anonymous letter, when a new development came to alter our
plans. Very early on the following morning I was aroused from my sleep by a tap
upon my bedroom door. It was a messenger with a note from Mortimer. “Do come round,” it said; “the matter is becoming more and more
extraordinary.”

When I obeyed his summons I found him pacing excitedly up and down the
central room, while the old soldier who guarded the premises stood with
military stiffness in a corner. “My dear Jackson,” he cried, “I am so delighted that you have come, for
this is a most inexplicable business.”

“What has happened, then?”

He waved his hand towards the case which contained the breastplate. “Look at it,” said he. I did so, and could not restrain a cry of surprise. The setting of the
middle row of precious stones had been profaned in the same manner as
the upper ones. Of the twelve jewels, eight had been now tampered with
in this singular fashion. The setting of the lower four was neat and
smooth. The others jagged and irregular. “Have the stones been altered?” I asked. “No, I am certain that these upper four are the same which the expert
pronounced to be genuine, for I observed yesterday that little
discoloration on the edge of the emerald. Since they have not extracted
the upper stones, there is no reason to think the lower have been
transposed. You say that you heard nothing, Simpson?”

“No, sir,” the commissionaire answered. “But when I made my round after
daylight I had a special look at these stones, and I saw at once that
some one had been meddling with them. Then I called you, sir, and told
you. I was backwards and forwards all the night, and I never saw a soul
or heard a sound.”

“Come up and have some breakfast with me,” said Mortimer, and he took me
into his own chambers.—“Now, what _do_ you think of this, Jackson?” he
asked. “It is the most objectless, futile, idiotic business that ever I heard
of. It can only be the work of a monomaniac.”

“Can you put forward any theory?”

A curious idea came into my head. “This object is a Jewish relic of
great antiquity and sanctity,” said I. “How about the anti-Semitic
movement? Could one conceive that a fanatic of that way of thinking
might desecrate——”

“No, no, no!” cried Mortimer. “That will never do! Such a man might push
his lunacy to the length of destroying a Jewish relic, but why on earth
should he nibble round every stone so carefully that he can only do four
stones in a night? We must have a better solution than that, and we must
find it for ourselves, for I do not think that our inspector is likely
to help us. First of all, what do you think of Simpson, the porter?”

“Have you any reason to suspect him?”

“Only that he is the one person on the premises.”

“But why should he indulge in such wanton destruction? Nothing has been
taken away. He has no motive.”

“Mania?”

“No, I will swear to his sanity.”

“Have you any other theory?”

“Well, yourself, for example. You are not a somnambulist, by any
chance?”

“Nothing of the sort, I assure you.”

“Then I give it up.”

“But I don’t—and I have a plan by which we will make it all clear.”

“To visit Professor Andreas?”

“No, we shall find our solution nearer than Scotland, I will tell you
what we shall do. You know that skylight which overlooks the central
hall? We will leave the electric lights in the hall, and we will keep
watch in the lumber-room, you and I, and solve the mystery for
ourselves. If our mysterious visitor is doing four stones at a time, he
has four still to do, and there is every reason to think that he will
return to-night and complete the job.”

“Excellent!” I cried. “We will keep our own secret, and say nothing either to the police or to
Simpson. Will you join me?”

“With the utmost pleasure,” said I; and so it was agreed. It was ten o’clock that night when I returned to the Belmore Street
Museum. Mortimer was, as I could see, in a state of suppressed nervous
excitement, but it was still too early to begin our vigil, so we
remained for an hour or so in his chambers, discussing all the
possibilities of the singular business which we had met to solve. At
last the roaring stream of hansom cabs and the rush of hurrying feet
became lower and more intermittent as the pleasure-seekers passed on
their way to their stations or their homes. It was nearly twelve when
Mortimer led the way to the lumber-room which overlooked the central
hall of the museum. He had visited it during the day, and had spread some sacking so that we
could lie at our ease, and look straight down into the museum. The
skylight was of unfrosted glass, but was so covered with dust that it
would be impossible for any one looking up from below to detect that he
was overlooked. We cleared a small piece at each corner, which gave us a
complete view of the room beneath us. In the cold white light of the
electric lamps everything stood out hard and clear, and I could see the
smallest detail of the contents of the various cases.