"Get away from that door!" yelled the enraged man. "What right have you to be prying into my affairs? I hired you to do copying work for me, not to roam about this house."

"Well, I'm done copying those illegal deeds for you!" retorted Mort. "And, what's more, we're going to find out whom you have a prisoner in there!"

"A prisoner? You are joking. There is no one in there."

"Yes, there is. He wrote an appeal for help on the typewriter and tossed the paper from the window. Hark, you can hear him calling for help!"

There was a moment's silence, but no cry came from behind the door, one panel of which was shattered.

"You see," sneered Muchmore. "I guess you'll wish you hadn't begun this work, my friend, before I'm through with you. You'll be in jail ere you are many hours older. As for you," went on the man, turning to Bert, "I warned you, once before, not to trespass on my property. I shall also make a complaint against you. Now, clear out, both of you!"

"Suppose I refuse to go?" asked Mort coolly.

"Then I'll throw you out. I paid you your wages to the end of the week. You can consider yourself dismissed. If you don't go--"

Muchmore paused, but there was such a fierce look on his face, as he strode toward Bert and the stenographer, that, though neither of them was a coward, they judged it best not to provoke the man too much.

"Oh, we'll go," replied the stenographer. "But I warn you that you haven't heard the last of this. This place will be searched, by the proper authorities, and that prisoner, whoever he is, will be released."

"There is no prisoner there," retorted Muchmore. "And I'd like to see the authorities here, or from anywhere else, search this house without my permission. A man's house is his castle, here as much as in England. Now you have my answer, and you can do your worst!"

"I'll inform Mr. Stockton," threatened Bert.

"Do, you young rascal, when you can find him," and, with a laugh, Muchmore motioned his two unwelcome visitors to leave.

"Well, we didn't find out much," remarked the stenographer, as he and Bert were descending the hill toward the village. "I'm afraid I made rather a mess of it. He came back unexpectedly."

"Maybe he never went away."

"Mrs. Blarcum said he was going to be gone all night."

"I believe she's in with him. But we certainly learned one thing. Some person is a prisoner in the house, and it's a man who wants to get out."

"And we'll help him," added Mort. "I'll inform the authorities in the morning."

"Where will you stay to-night?" asked Bert.

"I don't know. I guess I'll go to the hotel."

"It isn't a very good place. Better come to my house. There are only mother and I, and we have a spare room for you."

"You are very kind. I'll come."

Mrs. Dare welcomed the stenographer, and, after he and Bert had talked over the queer events of the evening, they went to bed, intending to start an official inquiry the first thing in the morning.

But fate took a hand in the matter, and the mystery was solved sooner than Bert or Mort expected it would be.

In the middle of the night there was an alarm of fire. It came from the box on the hill, near the Stockton mansion, and Bert, hearing the clanging of the bell on the tower, awoke with a start and began to dress.

"Where is the blaze?" asked Mort.

"Somewhere up near the house of mystery. I hope it isn't another false alarm."

"May I go with you?" asked the stenographer.

"Of course. Hurry."

Mort quickly dressed, and he and Bert, the latter making his usual promise to his mother that he would be careful, were soon hastening from the house, and toward the location of the box, where they would meet the engine.

"It's no false alarm!" exclaimed Mort, as they began to climb the hill leading to the big house.

"You're right. It's a fire, but it doesn't seem to be very big. The engine is there; I can hear the bell."

Bert and the stenographer had taken a short cut to the Stockton mansion, and, as they emerged from the woods, on that side of the house where Bert had picked up the mysterious message, they saw flames shooting from one of the windows.

"The fire is on the side of the house where the prisoner is!" cried Bert "It's in that secret corridor!"

"Maybe you'll have a chance to rescue him!" exclaimed the stenographer.

The fire had not gained much headway, and, under Bert's direction, a long ladder was procured, raised against the side of the house, and then, carrying the hose himself, the young chief ascended toward the blaze.

"Give me the stream!" called Bert to Cole, who was in charge of the engine.

From the nozzle came the white, frothy mixture. Bert directed it at the window through which the flames were coming.

"Don't you dare go in that hall!" shouted Muchmore, running from the side door of the house to the foot of the ladder. "The fire doesn't amount to much. You can put it out from where you are, young man. I never called your department out. The old woman got scared and sent in the alarm. It's only some rubbish burning."

"I'll do as I think best about putting the fire out," replied Bert.

"Don't you go in that corridor!" yelled Muchmore, who seemed frantic over something.

The chemical stream was already smothering the blaze, and Bert could go a little farther up the ladder. He continued on, coming right opposite the window. Then he knew it was the same casement from which the mysterious message had been thrown. He could look in now, and he saw that the fire came from a pile of rags and paper on the floor. He directed the chemical stream directly on them, and in a few seconds the last vestige of the blaze was out. But Bert did not descend.

He was peering into the dark corridor. Would he get a sight of the prisoner held there? He tried to pierce the darkness. Surely that was a movement, surely that was someone hurrying to the window.

Bert looked down. He caught one glimpse of Muchmore, in the light from a lantern Tom Donnell was carrying, rushing at the ladder, as if to upset it, and precipitate the boy on it to the ground, thirty feet below.

But in the same glance Bert saw his chums holding back the enraged man. There was another movement in the corridor. Then a gleam of light showed, and, to his surprise, Bert saw an old man, carrying a lamp, coming toward him. The man's hands were bleeding, his clothes were disheveled, and his hair and beard were matted, as if they had known neither comb nor brush for a long time.

"Save me! Save me!" cried the man. "Is the fire out? I started it to call help! I thought the firemen would come. Oh, save me!"

"You're all right," replied Bert. "There is no danger. The fire is all out."

"Yes, the fire is out. There is no danger from that. It is my rascally nephew whom I fear. Save me from him!"

"Your nephew? Who is he?" asked Bert, wondering what was about to happen.

"Alfred Muchmore. Have you seen him? Where is he? If he finds me talking to you, he'll lock me up again. He shoved me back in the room after I started the fire, but I broke through the door. See my hands! They are cut and bleeding!"

"Who are you?"

"Harris Stockton."

"............