rn," he said solemnly, "mistook
Coverly for you! The moment that Coates drove away, the signal was
given. It _must_ have been. We were back here a few minutes later,
_Now_ do you see?"

"I do not, Gatton! What are you driving at?"

"At this: The telephone call _must_ have been made from somewhere in
the immediate neighborhood! There wasn't time to do it otherwise. And
there is no public call office within a mile _which is open after
seven o'clock!"_

"Good heavens!" I cried. "At last I understand!"

Gatton looked at me, smiling in grim triumph; and:

"Dr. Damar Greefe has a residence somewhere within a quarter-mile
radius of this house!" he declared. "He has betrayed himself!
Then--look here."

Unscrewing the front of the mouthpiece of the false telephone, he took
out the strip of cardboard upon which my number was written, turned it
over ... and there upon the back was another number!

"Just look up Dr. Brown-Edwards," he said. "He was the last occupant
of the Red House, and may still be in the book."

Grasping the purpose of his inquiry, excitedly I did as he directed;
and there sure enough the number appeared!

"The identical instrument that was used at the Red House!" cried
Gatton. "Note the artistic finish with which even the _correct_
exchange numbers are looked up!"

I sank back in my chair, silent, appalled at the perverted genius of
this fiend whom we were pitted against in a life-or-death struggle.
But presently:

"What was the object of the opening and closing of the garage doors at
the Red House?" I asked, almost mechanically.

"Simple enough," Gatton replied. "Whereas here the telephone was
installed, so that the bell could be rung by some one merely calling
up your number--and the ringing stopped by the caller telling the
exchange he had made a mistake--in the Red House, as I have
discovered, the 'phone had been disconnected shortly after Dr.
Brown-Edwards left the place."

"Then the opening and closing of the doors was merely a device for
ringing the bell?"

"Yes. The opening of the first door set it ringing and the opening of
the second probably stopped it. Mr. Addison," he stood up, resting his
hands upon the table and regarding me fixedly--"we enter upon the
final battle of wits: New Scotland Yard _versus_ Dr. Damar Greefe and
the green-eyed lady of Bast. Regarding the latter--there is a very
significant point."

"What is that?"

"The 'voice' on this last occasion was that, not o