The student read what he had been noting in the next room. At the
production of the coat during the demonstration of the markings of the
bullet, Mrs. Parker had betrayed great emotion, Mr. Bruce had done
likewise, and nothing more than ordinary emotion had been noted for
the rest of us. Miss La Neige's automatic record during the tracing
out of the sending of the note to Parker had been especially
unfavorable to hear; Mr. Bruce showed almost as much excitement; Mrs.
Parker very little and Downey very little. It was all set forth in
curves drawn by self-recording pens on regular ruled paper. The
student had merely noted what took place in the lecture-room as
corresponding to these curves.

"At the mention of the noiseless gun," said Kennedy, bending over the
record, while the student pointed it out to him and we leaned forward
to catch his words, "I find that the curves of Miss La Neige, Mrs.
Parker, and Mr. Downey are only so far from normal as would be
natural. All of them were witnessing a thing for the first time with
only curiosity and no fear. The curve made by Mr. Bruce shows great
agitation and--"

I heard a metallic click at my side and turned hastily. It was
Inspector Barney O'Connor, who had stepped out of the shadow with a
pair of hand-cuffs.

"James Bruce, you are under arrest," he said.

There flashed on my mind, and I think on the minds of some of the
others a picture of another electrically wired chair.