ther inventions, or to stop you
from completing your latest--the aerial warship."

"But I didn't know the foreign governments knew about that," Tom
exclaimed. "It was a secret."

"Few secrets are safe from foreign Spies," declared Lieutenant Marbury.
"They have a great ferreting-out system on the other side. We are just
beginning to appreciate it. But our own men have not been idle."

"Have they really learned anything?" Tom asked. "Nothing definite
enough to warrant us in acting," was the answer of the government man.
"But we know enough to let us see that the plot is far-reaching."

"Are the French in it?" asked Ned impulsively.

"The French! Why do you ask that?"

"Tell him about Eradicate, and the man who wanted to buy the mule,
Tom," suggested Ned.

Thereupon the young inventor mentioned the story told by Eradicate. He
also brought out the fire-bomb, and explained his theory as to how it
had operated to set the red shed ablaze.

"I think you are right," said Lieutenant Marbury. "And, as regards the
French, I might say they are not the only nation banded to obtain our
secrets--yours and the government's!"

"But I thought the French and the English were friendly toward us!" Ned
exclaimed.

"So they are, in a certain measure," the officer went on. "And Russia
is, too. But, in all foreign countries there are two parties, the war
party, as it might be called, and the peace element.

"But I might add that it is neither France, England, nor Russia that we
must fear. It is a certain other great nation, which at present I will
not name."

"And you think spies set this fire?"

"I certainly do."

"But what measures shall I adopt against this plot?" Tom asked.

"We will talk that over," said Lieutenant Marbury. "But, before I go
into details, I want to give you another warning. You must be very
careful about--"

A sudden knock on the door interrupted the speaker.

CHAPTER IX

THE RECOIL CHECK

"Who is that?" asked Ned Newton, with a quick glance at his chum.

"I don't know," Tom answered. "I left orders we weren't to be disturbed
unless it was something important."

"May be something has happened," suggested the navy officer, "another
fire, perhaps, or a--"

"It isn't a fire," Tom answered. "The automatic alarm would be ringing
before this in that case."

The knock was repeated. Tom went softly to the door and opened it
quickly, to disclose, standing in the corridor, one of the messenger