But as he spoke he suddenly began to disappear through the floor and only by catching the edge of it did he save himself. He and Hortense were too surprised to speak for a moment. Then they knelt on the edge of the opening and peered down. "It's a trapdoor," said Andy. "We must find out where it goes." He pushed the door to one side and revealed a little staircase. "Are you afraid to go down?" Andy asked. "Of course not," said Hortense. "You go first." Andy led the way and Hortense followed. A few steps brought them to a small room. It was dark, but the light from the trapdoor enabled them to see a little after a while. There was nothing in the room but a large chest. "Shall we open it?" Andy asked. "Of course," said Hortense. By pulling and tugging they succeeded at last in lifting the lid. "It's empty," said Andy much disappointed. "I hoped it might be full of gold and jewels." Hortense had a sudden thought. "This is where Jeremiah went the time we couldn't find him." Andy was unconvinced. "A cat couldn't open a trapdoor," he said. "Maybe Jeremiah could. He's no ordinary cat. Besides there's another one." "Another cat?" Andy demanded. "No. Somebody else we haven't seen, but I can guess who it is." "Who is it?" "I won't tell yet--not until I'm sure. But we'll see him. Maybe we'll surprise him and Jeremiah here some night and take them captive." "Hello," said Andy as he put his foot on the stairs. "What's this?" Beside the chimney was a black hole and fastened to the chimney was an iron bar like the rung of a ladder. Andy peered down. "There's another rung," he said. "I wonder where this ladder goes?" "We'll have to find out," said Hortense. "Dear me, this is a most mysterious house." Andy put one foot on the ladder and began to descend. Soon his head disappeared from sight. "It goes down and down, probably to the basement," he called. "Come on." Hortense obeyed, and down and down they went. It was very dark, but now and then a little chink beside the chimney let in a ray of light. "Maybe it goes to the middle of the earth," said Andy from below. "No, here's the bottom at last." Soon Hortense stood behind him. Gradually, as their eyes became accustomed to the dark, they could see a little. "Here's the way," said Andy at last. "But here's another passage," said Hortense. "We'll try mine first," said Andy. They had walked only a few steps when they came to a wooden panel. "It's like the one that I crawled through the other day," said Andy. "Help me to move it." It moved slowly, but finally they raised it until they could crawl through. "I believe this is the chute I came down when you found me," said Andy. He stood up. "There's the basement window," he said, "and here's the little door I crawled through. Now we can get out." "We must see where the other way goes first," Hortense reminded him. "I'd forgotten," said Andy.