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.”