"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