"A sheet on which I did some figuring. It is no good, but it was in with
the plans. It must have dropped out."

"Do you mean that some one has been in here and taken the plans of your
new aeroplane, Tom?" gasped his father.

"That's just what I mean! They sneaked in here while you were dozing,
took the plans, and jumped out of the window with them. On the way this
paper fell out. It's the only clue we have. Stay here, dad. I'm going to
have a look." And Tom jumped from the library window and ran down the
path after the unknown thief.




Chapter Four

Anxious Days


Peering on all sides as he dashed along the gravel walk, hoping to catch
a glimpse of the unknown intruder in the garden or shrubbery, Tom
sprinted on at top speed. Now and then he paused to listen, but no sound
came to him to tell of some one in retreat before him. There was only
Silence.

"Mighty queer," mused the youth. "Whoever it was, he couldn't have had
more than a minute start of me--no, not even half a minute--and yet
they've disappeared as completely as though the ground had opened and
let them down; and the worst of it is, that they've taken my plans with