worried look on his face, followed his son. Mr. Sharp stood in the door of the shop.
"I thought I heard some one moving around back here," went on Tom quietly.
"Some one in this shop!" exclaimed the aged inventor excitedly. "Some one trying to steal my ideas again! Mr. Sharp, come here! Bring that rifle! We'll teach these scoundrels a lesson!"
Tom quickly darted back to the extreme rear of the building. There was a scuffle, and the next minute Tom cried out:
"What are you doing here?"
"Ha! I beg your pardon," replied a voice. "I am looking for Mr. Barton Swift."
"My father," remarked Tom. "But that's a queer place to look for him. He's up front. Father, here's a man who wishes to see you," he called.
"Yes, I strolled in, and seeing no one about I went to the rear of the place," the voice went on. "I hope I haven't transgressed."
"We were busy on the other side of the shop, I guess," replied Tom, and he looked suspiciously at the man who emerged from the darkness into the light from a window. "I beg your pardon for grabbing you the way I did," went on the lad, "but I thought you were one of a gang of men we've been having trouble with."
