w, this boy didn't drop into the river. He dropped the
provisions he bought for the boat into the coal mine, and left them
there for the consumption of the two boys inside. That's reasonable,
isn't it?"

"Fine deduction, as Sherlock Holmes would say to Watson!" laughed
George.

"But this third boy," Will went on, "doesn't go into the mine. He stays
outside to serve as a means of communication between the boys who are
hiding in the mine and some interested person or persons on the outside.
That's perfectly clear, isn't it?"

"That'll do very well for a theory," replied George.

"I'll go you a plate of cookies," argued Sandy, "that Will is right, and
that this third boy is hanging around taking messages from the two boys
in the mine and also to the two boys in the mine."

"Didn't I say it was all right for a theory?" chuckled George.

"Now, the point is this," Will continued. "What are those boys in the
mine for? What do they want there? Why didn't they answer our Boy Scout
challenge when we replied to their call of the pack?"

"If you don't ask so many questions, you won't get so many negative
answers," Sandy advised. "We're here to find the boys, and I don't see
that it makes any difference to us what they're in there for."

"But we've found the boys now," contended Tommy. "We haven't got our
hands on them yet, of course, but we know they're in there, and we know
it's only a question of time when we get hold of them."

"Well," Will insisted, "I'm going to find a motive before I quit the
case. I'm going to know who sent those boys here, and all about it,
before I make any report to Mr. Horton."

"Go as far as you like," laughed Tommy. "My bump of curiosity is growing
half an inch a day, and will continue to spread out until I find out
exactly what those boys are doing burrowing in a deserted mine."

"Now, we'll get back to the point we started from," Will explained.
"This boy who is undoubtedly doing duty outside the mine in the
interests of the persons who sent the two boys in, furnishes the clue to
the whole situation! When we find him, and find out what he's up to, and
trace any communications he may make back to their original source,
we'll have the whole case tied up tight!"

"That's right!" declared Tommy. "We'll have the case tied up tight if we
succeed in getting hold of this third boy."

"Oh, go on!" laughed Sandy. "We'll be picking third boys and fourth boys
and fifth boys out of the air, first t