“Excellent device. Nothing could be better.”

“A good move—​wasn’t it?”

“Oh, dear me, yes, most admirable.”

“I thought you would say so.”

“And so a post-mortem was made?”

“It was.”

“With what result?”

“It was clearly established, beyond all cavil, that the ill fated young woman had died from the effects of a mineral poison.”

When Mr. Shearman uttered these last words, he regarded his companion with a searching glance.

The doctor quailed before the piercing eyes of the detective. In appearance his face resembled that of a corpse rather than that of a living being.