"That's it," said Bob,--"stole the set of blue-prints we have been working from.  What's more, they must have seen the airplane before they got out.  I went to take the plans out of the bench drawer here where we have kept them locked up, and there was the drawer wide open, the lock picked, and the drawings gone.  I'll bet a herring we can thank my dark-skinned shadow of yesterday for this little visit!"