up in this."

"Maybe; but I doubt it. I tell you there isn't a clue leading to
Peters--as yet."

"But there will be," insisted Ned. "You'll see that that I'm right
this time."

"I can't see it, Ned. As a matter of fact, I would have gone to
Boylan about that button I found in my airship only I've been so
busy on this photo telephone, and in arranging the trap, that I
haven't had time. But if this fails--and I'm hoping it won't--I'll
get after him," and there was a grim look on the young inventor's
face.

It was wearying and nervous work--this waiting. Tom and Ned felt
the strain as they sat there in Mrs. Damon's library, near the
telephone. It had been fitted up in readiness. Attached to the
receiving wires was a sensitive plate, on which Tom hoped would be
imprinted the image of the man at the other end of the wire--the
criminal who, in exchange for the valuable land papers, would give
Mr. Damon his liberty.

There was also the phonograph cylinder to record the man's voice.
Several times, while waiting for the call to come in, Tom got up
to test the apparatus. It was in perfect working order.

As before, there was an extension telephone, so that Mrs. Damon
could talk to the unknown, while Tom could hear as well. But he
planned to take no part in the conversation unless something
unforeseen occurred.

Mr. Damon was an enthusiastic photographer, and he had a dark room
adjoining his library. It was in this dark room that Tom planned
to develop the photo telephone plate.

On this occasion he was not going to use the metal plate in which,
ordinarily, the image of the person talking appeared. That record
was but a fleeting one, as in a mirror. This time Tom wanted a
permanent picture that could, if necessary, be used in a court of
justice.

Tom's plan was this: If the person who had demanded the papers
came to one of the photo telephones, and spoke to Mrs. Damon, Tom
would switch on the receiving apparatus. Thus, while the man was
talking, his picture would be taken, though he would not know of
the thing being done.

His voice would also be recorded on the wax cylinder, and he would
be equally unaware of this.

When Tom had imprinted the fellow's image on the prepared plate,
he would go quickly to the dark room and develop it. A wet print
could be made, and with this as evidence, and to use in
identification, a quick trip could be made to the place whence the
man had telephoned. Tom hoped thus to capture hi