“As Samuel is promptly despatched to fresh meadows and pastures new!—Well, yes, Inspector, one must admit that’s a sound enough theory, and very cogently stated.”
“Doesn’t it seem to you the only reasonable theory, sir? Or at any rate, the most reasonable?”
“I suppose it does,” Roger said thoughtfully. “Yes, the most reasonable, without doubt. So now we come back to the good old problem, which I solved so extremely neatly last week—who killed Mrs. Vane?”
“We do, sir. And as to that, do you see one big fact in this second case which is going to give us a valuable pointer to the identity of the double murderer?”
“This is as good as a correspondence course,” Roger murmured: “ ‘How to Be a Detective,’ in three lessons—Yes, Teacher, I do. Aconitine.”
“That’s right, sir. It must have been somebody who had access to aconitine; I think we can take that for granted. I shall make enquiries at the chemist’s in Sandsea and elsewhere, of course, as a matter of form; but I don’t fancy they’ll lead to anything. The murderer knew all about poisons; that’s obvious. Something was wanted that would act quickly, so the choice was practically limited to prussic acid, strychnine, aconitine and curare. Prussic acid smells too strong, so the man could hardly be induced to take it unsuspectingly; with strychnine he’d shout out and make too much fuss; curare won’t act except on an open wound; aconitine (a big dose of aconitine, that is) was just what was wanted.”
“Humph!” Roger said seriously, stroking his chin. “I see what you’re getting at, of course. But do you really think he⸺”
“Hullo, you two!” said a voice from the door. “Still yapping? Hope you’ve got something to drink up here. I’ve got a throat like a mustard plaster after walking along that road in this heat.”
“Anthony,” said his cousin with not unjustified annoyance, “you’re gross.”
The conversation swerved abruptly from matters criminal.