She was so self-possessed, so unafraid in her attitude and expression of face, that I had no real reason to doubt her good faith. But I did, and I determined to watch Alma Remsen carefully and to the exclusion of everybody else connected with the mystery. Moreover, I determined to keep my knowledge to myself. I wasn’t sure whether I should tell Moore eventually or not, but at any rate, I wasn’t ready to tell him yet. After a few questions, which seemed to me of no real importance, Alma was excused and Mrs. Dallas was summoned. What a different type of woman! She was, as I learned later, about thirty, but her hair had turned prematurely gray, almost white. She wore it short, a soft, curly bob, that framed her young-looking face with a sort of halo. Her eyes were gray, too, with dark lashes, and her complexion was perfect. That lovely creamy flesh, with a soft sheen on it that needed, I felt sure, no aid of cosmetics. Her mouth was a Cupid’s bow, and her smile was that of a siren. I gazed at her, because I couldn’t tear my eyes away. True, I had seen her the night before at the Moores’ dinner party, but she hadn’t looked like this then. At the dinner she had seemed out of sorts, and unsmiling. Now, she was animated and fascinating. A strange idea came to me. Suppose she had killed Sampson Tracy, wouldn’t she adopt this attitude of charm to wheedle the Coroner? Then I laughed at my own foolishness. Why, of all people, would Katherine Dallas kill the man she was about to marry? The wealthy, powerful magnate, who was ready to dower her with everything heart could wish and put her at the head of his great establishment. Of course not. She had no motive, nor had she opportunity. Even if she possessed a latchkey, which might well be, she couldn’t come to the house in the dead of night, and get away again, without being seen by somebody. Although, I was forced to admit, whoever killed the man had gone to his room in the dead of night, and had got away again, unseen, so far as we could learn. How had he got away? Well, that question was as yet unanswered. Even now, I realized, Coroner Hart was asking Mrs. Dallas her opinion on this very matter. “I can’t imagine,” she said, and I was angry with myself to realize that her voice had in it no ring of a false note, no hint of insincerity. “It is too impossible,” she went on, her lovely face alight with interest, “whoever killed Mr. Tracy had to get out of that room and leave the door locked behind him, but how could he do it?” “Dived out of the window,” suggested Keeley, to hear what she would say. “Then he was a master diver,” she told him. “Deep Lake, or as they call it here, the Sunless Sea, is not only very deep, but it is full of hidden rocks and there are strong eddies and currents,—oh, it is a dangerous hole!” “There’s the alternative of a secret passage,” Moore went on. “Did you ever hear of one?”