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!"