s
astonished eyes even more terrifying than before.

With a bound he reached the rear window, and swung himself upon the fire
escape. There was no one in sight. The gray surface of the ironwork
showed not the slightest scratch, save those made by his own heels
earlier in the day. The steps of the ladder leading up to the next floor
were glistening, immaculate. Those of the one to the floor below were
equally so. He re-entered the room, and going to the opposite window,
threw it wide open. The three dormer windows of the adjoining house were
gray, dusty, as though they had not been opened for years. He turned to
his companion with a look of amazement.

"In all my experience, Mrs. Morton," he said, "I do not think that I
have ever encountered anything quite so astonishing. That letter must
have been placed there while I was in the apartment above. Your cook,
your maid, are out. Certainly you did not place it there yourself. And
yet we know that someone has been in this room, or at least delivered
the letter, during the past fifteen minutes. Had I not found it here
myself, I should have been almost tempted to disbelieve it, but I am
forced to admit its truth."

Mrs. Morton stood wringing her hands.

"It--it seems almost supernatural," she exclaimed. "Poor Ruth. What are
we to do?"

"There is nothing supernatural about the matter, madam," Duvall
remarked. "I don't doubt the explanation is simple enough, could we but
hit upon it. But so far I confess I am unable to understand it." He went
over to the wall which adjoined that of the house next door, and sounded
it, inch by inch, with a small hammer he took from his bag of tools. The
operation required several minutes. When he had completed it, he tossed
the hammer back into his kit in disgust. "Brick, of course," he said,
"and perfectly solid." He turned toward the door. "What are you going to
do now?" Mrs. Morton asked.

"Try to find out something through this telegram. And also, investigate
the house next door."

"But, you will come back? I am afraid."

"I shall be at your call at all times, Mrs. Morton. If anything of
interest occurs, notify me here." He drew a card from his pocket and
wrote upon it the name of his hotel. "Say nothing to your daughter about
these new threats. I shall probably see you again later in the day."
Shouldering his kit of tools, Duvall left the apartment. He was by no
means satisfied with the results of his visit. In fact there had
appa