“Well,” he said, “let us consider the facts in order.  Here is a man who, we assume, is under the influence of a poisonous dose of morphine.  The question is, did he take that dose himself or was it administered to him by some other person?  If he took it himself, with what object did he take it?  The history that was given to you seems completely to exclude the idea of suicide.  But the patient’s condition seems equally to exclude the idea of morphinomania.  Your opium-eater does not reduce himself to a state of coma.  He usually keeps well within the limits of the tolerance that has been established.  The conclusion that emerges is, I think, that the drug was administered by some other person; and the most likely person seems to be Mr. Weiss.”

“Isn’t morphine a very unusual poison?”

“Very; and most inconvenient except in a single, fatal dose, by reason of the rapidity with which tolerance of the drug is established.  But we must not forget that slow morphine poisoning might be eminently suitable in certain cases.  The manner in which it enfeebles the will, confuses the judgment and debilitates the body might make it very useful to a poisoner whose aim was to get some instrument or document executed, such as a will, deed or assignment.  And death could be produced afterwards by other means.  You see the important bearing of this?”

“You mean in respect of a death certificate?”

“Yes.  Suppose Mr. Weiss to have given a large dose of morphine.  He then sends for you and throws out a suggestion of sleeping sickness.  If you accept the suggestion he is pretty safe.  He can repeat the process until he kills his victim and then get a certificate from you which will cover the murder.  It was quite an ingenious scheme—­which, by the way, is characteristic of intricate crimes; your subtle criminal often plans his crime like a genius, but he generally executes it like a fool—­as this man seems to have done, if we are not doing him an injustice.”

“How has he acted like a fool?”

“In several respects.  In the first place, he should have chosen his doctor.  A good, brisk, confident man who ‘knows his own mind’ is the sort of person who would have suited him; a man who would have jumped at a diagnosis and stuck to it; or else an ignorant weakling of alcoholic tendencies.  It was shockingly bad luck to run against a cautious scientific practitioner like my learned friend.  Then, of course, all this secrecy was sheer tomfoolery, exactly calculated to put a careful man on his guard; as it has actually done.  If Mr. Weiss is really a criminal, he has mismanaged his affairs badly.”

“And you apparently think that he is a criminal?”

“I suspect him deeply.  But I should like to ask you one or two questions about him.  You say he spoke with a German accent.  What command of English had he?  Was his vocabulary good?  Did he use any German idioms?”

“No.  I should say that his English was perfect, and I noticed that his phrases were quite well chosen even for an Englishman.”