must not overlook that."

"I don't," replied the young inventor. "O'Malley has it in for
me. No doubt of that. But he could not be sure that I would be
hurt by the explosion he arranged for."

"True," said his father.

"The attempt was against my invention. And O'Malley was
doubtless urged to destroy the locomotive that I am building
because my success will aid Mr. Bartholomew and his railroad."

"Quite agreed," said Ned. "But--"

"But the important question," interrupted Tom, "is this: How
did the bomb get into the interior of the electric locomotive?
That is the first and most important problem. Its having been
done once warns us that it can be done again until our system of
guarding the works is changed."

"We have five watchmen on the job at night, and the gates are
never opened in the daytime to anybody for any purpose without a
pass," declared Ned. "I don't see how that fellow got in here
with the time bomb."

"Exactly. It shows that there is a fault in our system
somewhere," said Tom grimly. "We cannot surround the place at
night with an armed guard. It would cost too much. Even Koku
cannot be everywhere. And I have reason to know that he was
wandering about the stockade last night as usual."