Happening to examine my little case of drugs I noticed that my stock of digitoxin was very much diminished."
"Digitoxin," said Poirot, "is a heart poison, is it not?"
"Yes.
It is obtained from digitalis purpurea - the common foxglove. There are four active principles - digitalin - digitonin - digitalein - and digitoxin.
Of these, digitoxin is considered the most active poisonous constituent of digitalis leaves.
According to Kopp's experiments, it is from six to ten times stronger than digitalin or digitalein.
It is official in France - but not in the British Pharmacopoeia."
"And a large dose of digitoxin?"
Dr. Gerard said gravely: "A large dose of digitoxin thrown suddenly on the circulation by intravenous injection would cause sudden death by quick palsy of the heart.
It has been estimated that four milligrams might prove fatal to an adult man."
"And Mrs. Boynton already suffered with heart trouble?"
"Yes; as a matter of fact, she was actually taking a medicine containing digitalis."
"That," said Poirot, "is extremely interesting."
"D'you mean," asked Colonel Carbury, "that her death might have been attributed to an overdose of her own medicine?"
"That - yes. But I meant more than that.
In some senses," said Dr. Gerard, "digitalis may be considered a cumulative drug.
Moreover, as regards postmortem appearance, the active principles of the digitalis may destroy life and leave no appreciative sign."
Poirot nodded slow appreciation.
"Yes, that is clever - very clever. Almost impossible to prove satisfactorily to a jury.
Ah, but let me tell you, gentlemen, if this is a murder, it is a very clever murder!
The hypodermic replaced, the poison employed being one which the victim was already taking - the possibilities of a mistake - or accident - are overwhelming.
Oh, yes, there are brains here. There is thought - care - genius." For a moment he sat in silence, then he raised his head. "And yet, one thing puzzles me."
"What is that?"
"The theft of the hypodermic syringe."
"It was taken," said Dr. Gerard quickly.
"Taken - and returned?" "Yes."
"Odd," said Poirot. "Very odd.
Otherwise everything fits so well..."
Colonel Carbury looked at him curiously.
"Well?" he said. "What's your expert opinion? Was it murder - or wasn't it?"
Poirot held up a hand.
"One moment.
We have not yet arrived at that point.
There is still some evidence to consider."
"What evidence?
You've had it all."
"Ah! But this is evidence that I, Hercule Poirot, bring to you." He nodded his head and smiled a little at their two astonished faces. ''Yes it is droll, that!
That I, to whom you tell the story, should in return present you with a piece of evidence about which you do not know.
It was like this.
In the Solomon Hotel, one night, I go to the window to make sure it is closed - "
"Closed - or open?" asked Carbury.
"Closed," said Poirot firmly. "It was open, so naturally, I go to close it.
But before I do so, as my hand is on the latch, I hear a voice speaking - an agreeable voice, low and clear with a tremor in it of nervous excitement. I say to myself it is a voice I will know again. And what does it say, this voice?
It says these words:
'You do see, don't you, that she's got to be killed?'"
He paused. "At the moment, naturellement, I do not take those words as referring to a killing of flesh and blood.
I think it is an author or perhaps a playwright who speaks.
But now I am not so sure.
That is to say, I am sure it was nothing of the kind." Again he paused before saying: "Messieurs, I will tell you this - to the best of my knowledge and belief those words were spoken by a young man whom I saw later in the lounge of the hotel and who was, so they told me on inquiring, a young man of the name of Raymond Boynton."
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