away. Chances are,
he wonders what boys wearing khaki suits like the regular soldiers of
the army are up here for. You agree with me, don't you, Hugh?"

"It looks that way," admitted the other. "Here you see one of the
impressions has stopped short only a few inches from the door, as if
the man stood here listening before stepping in, after carefully
removing the piece of rope we fixed to hold the door shut from the
outside."

"But how do you know that that impression wasn't made twenty-four
hours ago?" asked Bud, who was sitting cross-legged close by and
listening to their talk, even while he worked at his broken wing tip.

"Nothing could be easier," replied Hugh. "Here's the foot mark I
purposely made when I came out of the cabin last, and you can see
that he stepped into the same place. That tells us he was here
_afterward_. Get that, don't you, Bud?"

"I'd be a donkey if I didn't, and not worthy of being called a scout,"
the other boy remarked with scathing emphasis. "Fact is, if my mind
wasn't so much wrapped up with this aeroplane stability device, I
couldn't have missed seeing that little trick myself if I'd looked
the ground over; because that happens to be one of the first things
I ever learned about tracking and trailing."

"Even if the sneak didn't get anything worth while," Ralph continued
indignantly, "the fact that they seem to be hanging out around here
seems to tell that they must have a good reason for it all. The more
I get to thinking about it, the less I feel like saying we'd better
let the thing alone because it doesn't concern us. When things come
to such a pass that unknown persons even sneak into your cabin in
your absence and steal what they believe to be valuable papers, it's
high time to take a hand in the business. And if while we're
wandering around here we happen to run across those two men, I'll
feel like asking what they mean by poking their noses into Bud's
private business."

"Hear! hear!" said Bud, pretending to clap his hands; "that's the
sort of a chum to stack up with. Ralph's the kind to stick to a
fellow through thick and thin. And please inform that taller
walking mystery for me, Ralph, that I feel like telling him to
his face that he's a thief. Will, too, if ever I get half a chance."

Pretty soon Hugh and Ralph changed the subject of conversation and
wandered off together, talking earnestly about the habits of
muskrats and mink and otter. It was pretty la