Naturally his glance and mine both flew to the opposite wall. A window was before us of an unusual size and make. Unlike any which had ever before come under my observation, it swung on a pivot, and, though shut at the present moment, might very easily, when opened, present its huge pane at an angle capable of catching reflections from some of the many mirrors decorating the reception-room situated diagonally across the hall. As all the doorways on this lower floor were of unusual width, an open path was offered, as it were, for these reflections to pass, making it possible for scenes to be imaged here which, to the persons involved, would seem as safe from any one’s scrutiny as if they were taking place in the adjoining house. As we realized this, a look passed between us of more than ordinary significance. Pointing to the window, the inspector turned to a group of waiters watching us from the other side of the room and asked if it had been opened that evening. The answer came quickly. “Yes, sir,—just before the—the—” “I understand,” broke in the inspector; and, leaning over me, he whispered: “Tell me again exactly what you thought you saw.” But I could add little to my former description. “Perhaps you can tell me this,” he kindly persisted. “Was the picture, when you saw it, on a level with your eye, or did you have to lift your head in order to see it?” “It was high up,—in the air, as it were. That seemed its oddest feature.” The inspector’s mouth took a satisfied curve. “Possibly I might identify the door and passage, if I saw them,” I suggested. “Certainly, certainly,” was his cheerful rejoinder; and, summoning one of his men, he was about to give some order, when his impulse changed, and he asked if I could draw. I assured him, in some surprise, that I was far from being an adept in that direction, but that possibly I might manage a rough sketch; whereupon he pulled a pad and pencil from his pocket and requested me to make some sort of attempt to reproduce, on paper, my memory of this passage and the door. My heart was beating violently, and the pencil shook in my hand, but I knew that it would not do for me to show any hesitation in fixing for all eyes what, unaccountably to myself, continued to be perfectly plain to my own. So I endeavored to do as he bade me, and succeeded, to some extent, for he uttered a slight ejaculation at one of its features, and, while duly expressing his thanks, honored me with a very sharp look. “Is this your first visit to this house?” he asked. “No; I have been here before.” “In the evening, or in the afternoon?” “In the afternoon.” “I am told that the main entrance is not in use to-night.” “No. A side door is provided for occasions like the present. Guests entering there find a special hall and staircase, by which they can reach the upstairs dressing-rooms, without crossing the main hall. Is that what you mean?” “Yes, that is what I mean.”