"This method of mine for identifying the real pearl, as you will see," I blandly went on, "is a very simple one. You merely take a match end and dip it in clear water. Then you let a drop of water fall on the pearl. If the stone is an imitation one the water-drop will spread and lie close to the surface. If the stone is genuine the drop will stand high and rounded, like a globe of quicksilver, and will shake with the minute vibrations which pass through any body not in perfect equilibrium." Before I had completed that speech the maid Felice had stepped into the room. She was a woman of about thirty, white-skinned, slender of figure, and decidedly foreign-looking. Her face was a clever one, though I promptly disliked an affectation of languor with which she strove to hide a spirit which was only too plainly alert. "I want you to fetch my jewel case from the boudoir safe," her mistress told her. "Bring everything in the box." I could not see the maid's face, for at that moment I was busy watching Wilkins. From that worthy, however, came no slightest sign of disturbance or wonder. "Here, madam?" the maid was asking. "Yes, here and at once, please," answered Beatrice Van Tuyl. Then she turned to me. "And since you're such a jewel expert you'll be able to tell me what's darkening those turquoises of mine." I dropped a lump of sugar into my coffee and sipped it. Wilkins opened a dark-wooded buffet humidor before me, and I picked out a slender-waisted Havana corseted in a band of gold. I suddenly looked up at the man as he stood at my side holding the blue-flamed little alcohol lamp for the contact of my waiting cigar end. "Wilkins, how did you get that scar?" I asked him, out of a clear sky. The wrist itself was covered by its cuff and sleeve end, but under them, I knew, was the telltale mark. "What scar, sir?" he asked, his politeness touched with an indulgent patience which seemed to imply that he was not altogether unused to facing gentlemen in unaccountably high spirits. "This one!" I said, catching his hand in mine and running the cuff back along the white forearm. Not one trace of either alarm or resentment could I see on that indecipherable countenance. I almost began to admire the man. In his way he was superb. "Oh, that, sir!" he exclaimed, with an almost offensively condoning glance at the Van Tuyls, as though inquiring whether or not he should reply to a question at once so personal and at the same time so out of place. "Tell him where you got it, Wilkins," said Beatrice Van Tuyl, so sharply that it practically amounted to a command. "I got it stopping Lord Entristle's brougham, madam, in London, seven years ago," was the quiet and unhesitating answer. "How?" sharply asked the woman.