"But come downstairs with us and have a cup of coffee first," Stone said; "you'll need it, as you say you've had no breakfast. Fibsy makes first-rate coffee, and I can tell you, Calhoun, you've a hard day before you." "Have you learned anything further?" I managed to stammer out as we went down to the basement room that they used as a dining-room now. "Yes; as I told you, walls have tongues, and the walls have given up the secret of how Mrs. Schuyler managed her two-sided existence." But he would not tell me the secret until I had been fortified with two cups of steaming Mocha, which fully justified his praise of Fibsy's culinary prowess. Fibsy himself said nothing beyond a brief "good morning," and the lad's eyes were red and his voice shook as he spoke. "I knew," Stone said, as we finished breakfast, "that there must be some means, some secret means of communication between the two houses, the Schuyler house and this. You see, the Schuyler house, fronting on Fifth Avenue, three doors from the corner, runs back a hundred feet, and abuts on the rear rooms of this house, which runs back from the side street. In a word, the two houses form a right angle, and the back wall of the Schuyler house is directly against the side wall of the rear rooms of this house. Therefore, I felt sure there must be an entrance from one house to the other, not perceivable to an observer. And, of course, it must be in Mrs. Schuyler's own rooms; it couldn't be in their dining-room or halls. A few questions made me realize that Miss Van Allen's boudoir was separated from Mrs. Schuyler's bath room by only the partition wall of the houses. And I said that wall must speak to me. And it did." We were now on our way upstairs, Stone ready at last to let me into the secret he had discovered. We went to Vicky's boudoir, and he continued: "You know you found the strand of gilt beads caught in this mirror frame. We all assumed Miss Van Allen had flirted it there as she dressed for her party, but I reasoned that it might have caught there as she escaped to the Schuyler house the night of the murder. Yes, she did escape this way--look." Stone touched a hidden spring and the mirror in the Florentine frame slid silently aside into the wall, leaving an aperture that without doubt led into the next house. The frame remained stationary, but the mirror slid away as a sliding door works, and so smoothly that there was absolutely no sound or jar.