[Illustration: A plan of the upper floor of the château, showing the right wing. A large hallway, labelled “Right Gallery,” runs east-west through the wing, and has doors to the lumber room and Mademoiselle Stangerson’s rooms. Branching off south from the right gallery is a hallway labelled “Winding Gallery,” which has doors to Rouletabille’s room and Frédéric Larsan’s room. A dot at the southern end of the winding gallery is labelled “1”. The right gallery has a dot labelled “2” on the west end, and a dot labelled “3” where the right wing meets the stairs to the ground floor. There is a dot labelled “4” just outside of a window of Mademoiselle Stangerson’s bedroom. The window at the south end of the winding gallery is labelled “5”. Just outside this window is a semi-circular area labelled “6”.] 1. Position where Rouletabille placed Frédéric Larsan. 2. Position where Rouletabille placed Daddy Jacques. 3. Position where Rouletabille placed Monsieur Stangerson. 4. Window by which Rouletabille entered. 5. Window found open by Rouletabille when he left the room. He re-closed it. All the other doors and windows were shut. 6. Terrace surmounting a projecting room on the ground-floor. Rouletabille motioned me to follow him up a magnificent flight of stairs ending in a landing on the first floor. From this landing one could pass to the right or left wing of the château by a gallery opening from it. This gallery, high and wide, extended along the whole length of the building and was lit from the front of the château facing the north. The rooms, the windows of which looked to the south, opened out of the gallery. Professor Stangerson inhabited the left wing of the building. Mademoiselle Stangerson had her apartment in the right wing. We entered the gallery to the right. A narrow carpet, laid on the waxed oaken floor, which shone like glass, deadened the sound of our footsteps. Rouletabille asked me, in a low tone, to walk carefully, as we were passing the door of Mademoiselle Stangerson’s apartment. This consisted of a bed-room, an ante-room, a small bath-room, a boudoir, and a drawing-room. One could pass from one to another of these rooms without having to go by way of the gallery. The gallery continued straight to the western end of the building, where it was lit by a high window (window 2 on the plan). At about two-thirds of its length this gallery, at a right angle, joined another gallery following the course of the right wing. The better to follow this narrative, we shall call the gallery leading from the stairs to the eastern window, the “right” gallery and the gallery quitting it at a right angle, the “off-turning” gallery (winding gallery in the plan). It was at the meeting point of the two galleries that Rouletabille had his chamber, adjoining that of Frédéric Larsan, the door of each opening on to the “off-turning” gallery, while the doors of Mademoiselle Stangerson’s apartment opened into the “right” gallery. (See the Plan.)