There was a flash of fire and a deafening report as Tom fired.  The cloud of smoke obscured his vision for a moment, and as the echoes died away Tom could hear Mrs. Baggert screaming in her room.

“It’s all right!” cried the young inventor reassuringly.  “No one is hurt, Mrs. Baggert!” Then he flashed his light on the spot where the burglar had crouched.  As the smoke rolled away Tom peered in vain for a sight of the intruder.

Happy Harry was gone!

Holding his rifle in readiness, in case he should be attacked from some unexpected quarter, Tom strode forward.  He flashed his light in every direction.  There was no doubt about it.  The intruder had fled.  Taking advantage of the noise when the gun was fired, and under cover of the smoke, the burglar had leaped from the open window.  Tom guessed as much.  He hurried to the casement and peered out, at the same time noticing the cut wire of the burglar alarm.  It was quite dark, and he fancied he could hear the noise of some one running rapidly.  Aiming his rifle into the air, he fired again, at the same time crying out: 

“Hold on!”

“All right, Master Tom, I’m coming!” called the voice of the engineer from his shack.  “Are you hurt?  Is Mrs. Baggert murdered?  I hear her screaming.”

“That’s pretty good evidence that she isn’t murdered,” said Tom with a grim smile.

“Are you hurt?” again called Mr. Jackson.

“No, I’m all right,” answered Tom.  “Did you see any one running away as you came up?”

“No, Master Tom, I didn’t.  What happened?”

“A burglar got in, and I had him cornered, but he got away when I fired to arouse you.”

By this time the engineer was at the stoop, on which the window opened.  Tom unlocked a side door and admitted Mr. Jackson, and then, the incandescent light having been turned on, the two looked around the apartment.  Nothing in it had been disturbed, and the safe had not been opened.

“I heard him just in time,” commented Tom, telling the engineer what had happened.  “I wish I had thought to get between him and the window.  Then he couldn’t have gotten away.”

“He might have injured you, though,” said Mr. Jackson.  “We’ll go outside now, and look—­”

“Is any one killed?  Are you both murdered?” cried Mrs. Baggert at the dining-room door.  “If any one is killed I’m not coming in there.  I can’t bear the sight of blood.”

“No one is hurt,” declared Tom with a laugh.  “Come on in, Mrs. Baggert,” and the housekeeper entered, her hair all done up in curl papers.

“Oh, my goodness me!” she exclaimed.  “When I heard that cannon go off I was sure the house was coming down.  How is it some one wasn’t killed?”

“That wasn’t a cannon; it was only my little rifle,” said Tom, and then he told again, for the benefit of the housekeeper, the story of what had happened.

“We’d better hurry and look around the premises,” suggested Mr. Jackson.  “Maybe he is hiding, and will come back, or perhaps he has some confederates on the watch.”