laboratory that night,
one of the largest he had ever had. Mr. and Mrs. Wainwright and Miss
Marian came, the ladies heavily veiled. Doctor Nott and Mr. Whitney were
among the first to arrive. Later came Mr. Vanderdyke and last of all
Mrs. Ralston with Inspector O'Connor. Altogether it was an unwilling
party.

"I shall begin," said Kennedy, "by going over, briefly, the facts in
this case."

Tersely he summarised it, to my surprise laying great stress on the
proof that the couple had been asphyxiated.

"But it was no ordinary asphyxiation," he continued. "We have to deal in
this case with a poison which is apparently among the most subtle known.
A particle of matter so minute as to be hardly distinguishable by the
naked eye, on the point of a needle or a lancet, a prick of the skin
scarcely felt under any circumstances and which would pass quite
unheeded if the attention were otherwise engaged, and not all the power
in the world--unless one was fully prepared--could save the life of the
person in whose skin the puncture had been made."

Craig paused a moment, but no one showed any evidence of being more than
ordinarily impressed.

"This poison, I find, acts on the so-called endplates of the muscles and
nerves. It produces complete paralysis, but not loss of consciousness,
sensation, circulation, or respiration until the end approaches. It
seems to be one of the most powerful sedatives I have ever heard of.
When introduced in even a minute quantity it produces death finally by
asphyxiation--by paralysing the muscles of respiration. This asphyxia is
what so puzzled the coroner.

"I will now inject a little of the blood serum of the victims into a
white mouse."

He took a mouse from the box I had seen, and with a needle injected the
serum. The mouse did not even wince, so lightly did he touch it, but as
we watched, its life seemed gently to ebb away, without pain and without
struggle. Its breath simply seemed to stop.

Next he took the gourd I had seen on the table and with a knife scraped
off just the minutest particle of the black licorice-like stuff that
encrusted it. He dissolved the particle in some alcohol and with a
sterilised needle repeated his experiment on a second mouse. The effect
was precisely similar to that produced by the blood on the first.

It did not seem to me that anyone showed any emotion except possibly
the slight exclamation that escaped Miss Marian Wainwright. I fell
to wondering whether