In an hour more the last spark had been extinguished, and the chief gave orders for the engines to go back to quarters. It was the worst fire they had yet undertaken to fight, and the new engines had proved their efficiency in no uncertain manner. Little was talked of in town, the next day, but the fire and the sensational rescue. As for Bert and his chums, they, too, had a fruitful subject for conversation. They had learned much from their experience at the box factory blaze, which was liable to stand them in good stead at future fires. "I heard about you," remarked Mort Decker to Bert, when the next night he called at Cole's barn. "First thing you know you'll be getting offers from some big city department." "Oh, I guess not. But how are things at the house of mystery? Have you discovered anything new?" The two had walked out from the barn, to converse alone. "I don't like the way things are going," replied the stenographer. "Muchmore gave me several other deeds to copy to-day, and in some he had me change the descriptions and names. I don't like it. I'm sure, now, that he is a crook." "Can you do anything?" "That's just what I was thinking about. I have an idea he has some person a prisoner on that top floor, whom he is holding there until that person does as he wants, in the matter of some property." "If we could only get word to Mr. Stockton," said Bert, "he might call in the authorities." "Yes, if we could, that would be the very thing. But I don't know how to do it. I wrote him a letter, and mailed it in the post-office, but a little later I saw it on Muchmore's table. He must get Mr. Stockton's mail, and forward it. And now I think Muchmore suspects me, because he probably opened that letter I wrote to his uncle. So we may as well take the bull by the horns, and do something." "Yes; but what?" Mort looked around to see that no one would overhear him. "I'm going to make a try to get on that top floor," he said, "and I want you to help me." "When are you going to do it?" "To-night, in a little while. Muchmore is away, and there's nobody but the housekeeper there. We'll see who that mysterious prisoner is, who sends out typewritten messages asking for help. Will you come?" "Sure. I don't have to stay here. It's my night off." "Then come up to the Stockton mansion in about an hour. Go to the side door, knock three times, then a pause, then twice, and I'll know it's you, and let you in. We'll see if we can't solve the mystery." About an hour after this conversation Bert knocked at the door of the big house as directed. The place seemed deserted, and there was not a ray of light to be seen. "I wonder if he's here, or if Muchmore found out what he was up to, and drove him out," thought Bert, as he waited for an answer. But in a few minutes the stenographer admitted him.