I was not long in following his directions, but I found when I arrived that he had already returned with a police inspector, and another elderly gentleman, who proved to be Mr. Purvis, one of the partners of Morson and Company, the well-known diamond merchants. As an expert in stones he was always prepared to advise the police. They were grouped round the case in which the breast-plate of the Jewish priest had been exposed. The plate had been taken out and laid upon the glass top of the case, and the three heads were bent over it. "It is obvious that it has been tampered with," said Mortimer. "It caught my eye the moment that I passed through the room this morning. I examined it yesterday evening, so that it is certain that this has happened during the night." It was, as he had said, obvious that someone had been at work upon it. The settings of the uppermost row of four stones--the carnelian, peridot, emerald, and ruby--were rough and jagged as if someone had scraped all round them. The stones were in their places, but the beautiful gold work which we had admired only a few days before had been very clumsily pulled about. "It looks to me," said the police inspector, "as if someone had been trying to take out the stones." "My fear is," said Mortimer, "that he not only tried, but succeeded. I believe these four stones to be skilful imitations which have been put in the place of the originals." The same suspicion had evidently been in the mind of the expert, for he had been carefully examining the four stones with the aid of a lens. He now submitted them to several tests, and finally turned cheerfully to Mortimer. "I congratulate you, sir," said he, heartily. "I will pledge my reputation that all four of these stones are genuine, and of a most unusual degree of purity." The colour began to come back to my poor friend's frightened face, and he drew a long breath of relief. "Thank God!" he cried, "Then what in the world did the thief want?" "Probably he meant to take the stones, but was interrupted." "In that case one would expect him to take them out one at a time, but the setting of each of these has been loosened, and 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 into the museum?" "There is the door into Mr. Ward Mortimer's private rooms."