. He said:

"Oh! By the way, gentlemen, you need not either of you study up
chemistry, as did Mr. Munson. You remember the case? I know enough
chemistry for any experts that they may introduce, and will formulate
the main lines of their cross-examination myself. Let me refer to a
point that you made. Did I understand you that if we can show that
Mabel died of diphtheria, our case is won?"

"Why, certainly, Doctor. If we can prove that, we show that she died a
natural death."

"Of course, I understood that. I merely wished to show you what a
simple thing our defence is. We will convince the jury of that. I will
meet you at the office of the District Attorney at eleven o'clock on
the day after to-morrow. Good-morning, gentlemen." The Doctor bowed
and left the room. The two lawyers looked at one another a moment, and
then Mr. Dudley spoke:

"What a singular man!"

"The most extraordinary man I ever met!"

"Robert, why did you start to leave the room?"

"Mortimer, that is a very curious thing. I had a sort of premonition
that he would go away without leaving his address. I meant to instruct
Barnes to shadow him, when he should leave. I wonder if he read my
thoughts?"

"Rubbish! But why not send Jack after him now? He will catch up with
him easily enough."

Acting upon the suggestion, Mr. Bliss went into the outer office, and
was annoyed to be told by the office boy that Jack Barnes had gone out
half an hour before.

CHAPTER II.

JACK BARNES INVESTIGATES.

Jack Barnes, at this time, had just attained his majority. He was
studying law with Messrs. Dudley & Bliss, and acting as their office
assistant. But it was by no means his intention ever to practise the
profession, which he was acquiring with much assiduity. His one
ambition was to be a detective. Gifted with a keen, logical mind, a
strong disposition to study and solve problems, and possessing the
rare faculty of never forgetting a face, or a voice, he thought
himself endowed by nature with exactly the faculties necessary to make
a successful detective. His study of law was but a preliminary, which,
he rightly deemed, would be of value to him.

Anxious, as he was, to try his wits against some noted criminal, the
chance had never been his to make the effort. He had indeed ferreted
out one or two so-called "mysterious cases," but these had been in a
small country village, where a victory over the dull-witted
constabulary had counted for little in