e.

A single glance at the point of the steel rod made the whole thing
clear, and I gave a whistle of consternation; for the "rod" was a fine
tube with a sharply pointed end.

"The infernal scoundrel!" I exclaimed; "it is a hypodermic needle."

"Yes. A veterinary hypodermic, of extra large bore. Now you see the
subtlety and ingenuity of the whole thing. If he had had a reasonable
chance he would certainly have succeeded."

"You speak quite regretfully," I said, laughing again at the oddity of
his attitude towards the assassin.

"Not at all," he replied. "I have the character of a single-handed
player, but even the most self-reliant man can hardly make a
_post-mortem_ on himself. I am merely appreciating an admirable piece of
mechanical design most efficiently carried out. Observe the
completeness of the thing, and the way in which all the necessities of
the case are foreseen and met. This projectile was discharged from a
powerful air-gun--the walking-stick form--provided with a force-pump and
key. The barrel of that gun was rifled."

"How do you know that?" I asked.

"Well, to begin with, it would be useless to fit a needle to the
projectile unless the latter was made to travel with the point forwards;
but there is direct evidence that the barrel was rifled. You notice the
little square projection on the back surface of the cylinder. That was
evidently made to fit a washer or wad--probably a thin plate of soft
metal which would be driven by the pressure from behind into the grooves
of the rifling and thus give a spinning motion to the bullet. When the
latter left the barrel, the wad would drop off, leaving it free."

"I see. I was wondering what the square projection was for. It is, as
you say, extremely ingenious."

"Highly ingenious," said Thorndyke, enthusiastically, "and so is the
whole device. See how perfectly it would have worked but for a mere
fluke and for the complication of your presence. Supposing that I had
been alone, so that he could have approached to a shorter distance. In
that case he would not have missed, and the thing would have been done.
You see how it was intended to be done, I suppose?"

"I think so," I answered; "but I should like to hear your account of the
process."

"Well, you see, he first finds out that I am returning by a late
train--which he seems to have done--and he waits for me at the terminus.
Meanwhile he fills the cylinder with a solution of a powerful alkaloidal
pois