"We have apparently but four solutions; either one of the three women took the stud, or else the alleged loser lies. I omit the possibility that the stud was merely mislaid or accidentally out of sight in the room; this, because I personally conducted a search, which was so systematic as to make it absolutely assured that the stud was not in the room when I looked for it.
"Of the four theories, then, I preferred first to consider that one which the mistress declared to be ridiculous. I insisted upon seeing and catechising the maid Janet, thereby deepening madame's doubts as to my ability. After talking with this girl for half an hour, I felt so convinced of her integrity that I mentally eliminated her from the case. Next in order we had the two visitors, one of whom, according to Mrs. Upton, had a motive while the other had the opportunity. The first postulate always is that the guilty person must have both opportunity and motive, unless indeed we are dealing with an insane person, when motive may be eliminated, though frequently the insane are actuated by quite intelligible motives. Thus we seemed obliged either to discover that Mrs. Beaumont had an opportunity to obtain possession of the stud, or else that Mrs. Merivale had a motive, except that the latter may have simply acted upon the opportunity without motive, in which case we would be dealing with the kleptomaniac. After due consideration I decided to call separately upon these two ladies, and went to Mrs. Merivale first.
"She courteously received me, and as soon as I met her I was pleasantly impressed by her personality. After five minutes' talk I was certain that if she took the stud, it was, after all, the act of a kleptomaniac, and that no petty motive of revenge would have tempted this high-born, beautiful gentlewoman to descend to theft. She asked me the object of my call, and looked at me so frankly that there was no chance for subterfuge. Consequently I openly declared the purpose of my visit.
"'Madame,' said I, 'I regret very much the embarrassing nature of my errand. But you visited Mrs. Upton this morning, I believe?'
"'I did, in company with my cousin, Mrs. Beaumont.'
"'Did you happen to notice that while you were there she placed a diamond stud on the tea-table?'
"'Yes; I remember the circumstance perfectly, because of the impression which it made upon me.'
"'Would you mind telling me what that impression was?'
"'Why, simply that it was very discourteous, or at least very untidy. When we were shown to her room, she was lying down, with the collar of her waist open. After a while she arose, the stud dropped to the floor, and she picked it up and placed it on the little tea-table. I thought that it would have shown a greater sense of propriety if she had replaced it and fastened her collar.'
"'Do you recall whether the stud was still on the table when you left?'