le going down to the
studio this afternoon, I worked out and wrote down in my notebook the
particular features which appear in all these letters." He took a small
leather-covered book from his pocket.

"In the first place," he said, "the letter 'a' throughout the several
communications is always found to be out of line. The key bar is
doubtless a trifle bent. Let us, therefore, see if, in any of the
samples you have brought me, there exists a similar defect."

He took the samples of writing, one by one, and after scrutinizing them
carefully, passed them over to Baker, who likewise subjected them to a
critical examination. When their work was completed, it was found that
of the thirty-two samples, the displacement of the letter "a" occurred
in but three, and in one of these it was so slight as to be scarcely
noticeable. Duvall laid the three pages to one side. "A second fault
shown in the typewriting of the letters," he said, "is to be found in
the capital 'W.' Its lower right-hand corner has been worn or broken
off, so that it invariably fails to register." He handed one of the
letters to Baker. "See here, and here. The corner of the 'W' instead of
being clear and distinct, is blunt and defective. Let us see whether a
similar fault is to be found in any one of these three samples." He
picked up the three sheets of paper that he had placed to one side.

As he examined them, Mr. Baker and Mrs. Morton saw a shadow of
disappointment cross his face. He handed the three pages to Baker.

"The threatening letters were not written on any machine at your
studio," he said.

Baker took the pages and looked them over carefully.

"No," he said at length. "You are right. None of these show the second
defect you have named."

"Well," observed Duvall cheerfully, "we have accomplished something, at
least. We know that these letters were not written at the studio, and it
seems reasonably certain that the woman we are looking for has a
typewriter in her rooms, or wherever she may live. Of course she might
have had the typewriting done by some public stenographer, but I
consider it unlikely. A person sending threats of this character would
not be apt to entrust so dangerous a secret to a third person. We must
therefore make up our minds to find a woman who has a typewriting
machine, and knows how to use it."

"There are probably a hundred thousand such women in New York," Baker
observed, gloomily.

"No doubt. But we have more inf