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."