us.
What is it all about? Is some one trying to blow up the big dam?"

Nestor looked into the faces of the boys with serious eyes. He had not
suspected that they knew anything definite regarding the secret mission,
and was annoyed to think that he in part might be to blame for the leak
which had been discovered.

"Is that what you're going for?" asked Harry Stevens. "Are you going to
mix with governmental affairs again? Because we've got to go if you are.
Honest, now, we won't say a word if you tell us."

"Do you all promise that?" asked Nestor.

"Sure we do," came in chorus.

"Well, then," Nestor went on, "we don't know much about the matter, except
that there are hostile influences at work down there, directed against the
canal. We do not know the proposed point of attack, but presume that the
big dam is in the greatest danger. We do not even know where to look for
the plotters, or whether they are Americans or of foreign birth. The
motive for the contemplated destruction of the great waterway is not even
surmised. In fact, for all we know, this may be a scare, but the thing is
serious enough to call for rigid investigation, so down there we go."

"Sure you can't get along without us!" cried Jimmie. "If you want to know
who is at the bottom of it all, just ask me. It's the railroads. I've
heard men say the canal would have been finished years ago only for the
determined opposition of the transcontinental lines."

"Much you know about it!" cried Harry Stevens. "If anybody should ask you
where to look for the trouble, put your finger on the map of Japan. The
little brown men are digging under the Gatun dam if any one is."

"It does not seem possible that either the Japanese government or the
railroad interests would descend to such despicable work," Nestor said. "I
won't believe it of either of them until I have absolute proof."

"It would be going some to blow up the Gatun dam," Peter Fenton cut in.
"Why, when finished, that dam will be more than a hundred feet high, and
will cover one hundred and sixty-four square miles with water. Its purpose
is to huddle the highland streams into a lake which will become a part of
the canal. This lake will cover plantations, small farms, villages, and
even the present right of way of the Panama railroad."

"If they succeed in blowing up the Gatun dam," Jack said, "there will be
no Canal Completion Exposition in San Francisco in four years. That would
be a shame, for we we