He was locked in whenever Nôtredame went out; and in this way he spent many solitary and fearful hours. These led him, however, in the end, to a discovery. One day, about the middle of December, while he was poking about the house in the astrologer's absence, he found a door. I say "found," for though it was not a secret door, it was small and difficult to detect, being placed in the side of the straight, narrow passage at the head of the little staircase which led from the lower to the upper chambers. At first he thought it was locked, but coming to examine it more closely, though in mere curiosity, he found the handle of the latch let into a hollow of the panel. He pressed this, and the door yielded a little. At the time the boy was scared. He saw the place was dark, drew the door to the jamb again, and went away without satisfying his curiosity. But in a little while the desire to know what was behind the door overcame his terror. He returned with a taper, and, pressing the latch again, pushed the door open and entered, his heart beating loudly. He held up his taper, and saw a very narrow, bare closet, made in the thickness of the wall. And that was all, for the place was empty--the one and only thing it contained being a soft, rough mat which covered the floor. The boy stared fearfully about him, still expecting something dreadful, but there was nothing else to be seen. And gradually his fears subsided, and his curiosity with them, and he went out again. Another day, however, when he came into this place, he made a discovery. Against either wall he saw a morsel of black cloth fastened--a little flap a few inches long and three inches wide. He held the light first to one and then to another of these, but he could make nothing of them until he noticed that the lower edges were loose. Then he raised one. It disclosed a long, narrow slit, through which he could see the laboratory, with the fire burning dully, the phials glistening, and the crocodile going through its unceasing pretence of arousing itself. He raised the other, and found a slit there, too; but as the chamber on that side--the room with the astrolabe--was in darkness, he could see nothing. He understood, however. The closet was a spying-place, and these were Judas-holes, so arranged that the occupant, himself unheard and unseen, could see and hear all that happened on either side of him.