remember”—he addressed us collectively again—“that through all the tumult and noise next door Mademoiselle Cynthia slept. That admitted of two possibilities. Either her sleep was feigned—which I did not believe—or her unconsciousness was indeed by artificial means.
“With this latter idea in my mind, I examined all the coffee-cups most carefully, remembering that it was Mrs. Cavendish who had brought Mademoiselle Cynthia her coffee the night before. I took a sample from each cup, and had them analysed—with no result. I had counted the cups carefully, in the event of one having been removed. Six persons had taken coffee, and six cups were duly found. I had to confess myself mistaken.
“Then I discovered that I had been guilty of a very grave oversight. Coffee had been brought in for seven persons, not six, for Dr. Bauerstein had been there that evening. This changed the face of the whole affair, for there was now one cup missing. The servants noticed nothing, since Annie, the housemaid, who took in the coffee, brought in seven cups, not knowing that Mr. Inglethorp never drank it, whereas Dorcas, who cleared them away the following morning, found six as usual—or strictly speaking she found five, the sixth being the one found broken in Mrs. Inglethorp’s room.
“I was confident that the missing cup was that of Mademoiselle Cynthia. I had an additional reason for that belief in the fact that all the cups found contained sugar, which Mademoiselle Cynthia never took in her coffee. My attention was attracted by the story of Annie about some ‘salt’ on the tray of coco which she took every night to Mrs. Inglethorp’s room. I accordingly secured a sample of that coco, and sent it to be analysed.”
“But that had already been done by Dr. Bauerstein,” said Lawrence quickly.
“Not exactly. The analyst was asked by him to report whether strychnine was, or was not, present. He did not have it tested, as I did, for a narcotic.”
“For a narcotic?”
“Yes. Here is the analyst’s report. Mrs. Cavendish administered a safe, but effectual, narcotic to both Mrs. Inglethorp and Mademoiselle Cynthia. And it is possible that she had a mauvais quart d’heure in consequence! Imagine her feelings when her mother-in-law is suddenly taken ill and dies, and immediately after she hears the word ‘Poison’! She has believed that the sleeping draught she administered was perfectly harmless, but there is no doubt that for one terrible moment she must have feared that Mrs. Inglethorp’s death lay at her door. She is seized with panic, and under its influence she hurries downstairs, and quickly drops the coffee-cup and saucer used by Mademoiselle Cynthia into a large brass vase, where it is discovered later by Monsieur Lawrence. The remains of the coco she dare not touch. Too many eyes are upon her. Guess at her relief when strychnine is mentioned, and she discovers that after all the tragedy is not her doing.
“We are now able to account for the symptoms of strychnine poisoning being so long in making their appearance. A narcotic taken with strychnine will delay the action of the poison for some hours.”
Poirot paused. Mary looked up at him, the colour slowly rising in her face.
“All you have said is quite true, Monsieur Poirot. It was the most awful hour of my life. I shall never forget it. But you are wonderful. I understand now——”
“What I meant when I told you that you could safely confess to Papa Poirot, eh? But you would not trust me.”
“I see everything now,” said Lawrence. “The drugged coco, taken on top of the poisoned coffee, amply accounts for the delay.”
“Exactly. But was the coffee poisoned, or was it not? We come to a little difficulty here, since Mrs. Inglethorp never drank it.”
“What?” The cry of surprise was universal.
“No. You will remember my speaking of a stain on the carpet in Mrs. Inglethorp’s room? There were some peculiar points about that stain. It was still damp, it exhaled a strong odour of coffee, and imbedded in the nap of the carpet I found some little splinters of china. What had happened was plain to me, for not two minutes before I had placed my little case on the table near the window, and the table, tilting up, had deposited it upon the floor on precisely the identical spot. In exactly the same way, Mrs. Inglethorp had laid down her cup of coffee on reaching her room the night before, and the treacherous table had played her the same trick.
“What happened next is mere guess work on my part, but I should say that Mrs. Inglethorp picked up the broken cup and placed it on the table by the bed. Feeling in need of a stimulant of some kind, she heated up her coco, and drank it off then and there. Now we are faced with a new problem. We know the coco contained no strychnine. The coffee was never drunk. Yet the strychnine must have been administered between seven and nine o’clock that evening. What third medium was there—a medium so suitable for disguising the taste of strychnine that it is extraordinary no one has thought of it?” Poirot looked round the room, and then answered himself impressively. “Her medicine!”
“Do you mean that the murderer introduced the strychnine into her tonic?” I cried.
“There was no need to introduce it. It was already there—in the mixture. The strychnine that killed Mrs. Inglethorp was the identical strychnine prescribed by Dr. Wilkins. To make that clear to you, I will read you an extract from a book on dispensing which I found in the Dispensary of the Red Cross Hospital at Tadminster:
“‘The following prescription has become famous in text books: Strychninae Sulph … … gr.I Potass Bromide … … . 3vi Aqua ad … … … . . 3viii Fiat Mistura
This solution deposits in a few hours the greater part of the strychnine salt as an insoluble bromide in transparent crystals. A lady in England lost her life by taking a similar mixture: the precipitated strychnine collected at the bottom, and in taking the last dose she swallowed nearly all of it!”
“Now there was, of course, no bromide in Dr. Wilkins’ prescription, but you will remember that I mentioned an empty box of bromide powders. One or two of those powders introduced into the full bottle of medicine would effectually precipitate the strychnine, as the book describes, and cause it to be taken in the last dose. You will learn later that the person who usually poured out Mrs. Inglethorp’s medicine was always extremely careful not to shake the bottle, but to leave the sediment at the bottom of it undisturbed.
“Throughout the case, there have been evidences that the tragedy was intended to take place on Monday evening. On that day, Mrs. Inglethorp’s bell wire was neatly cut, and on Monday evening Mademoiselle Cynthia was spending the night with friends, so that Mrs. Inglethorp would have been quite alone in the right wing, completely shut off from help of any kind, and would have died, in all probability, before medical aid could have been summoned. But in her hurry to be in time for the village entertainment Mrs. Inglethorp forgot to take her medicine, and the next day she lunched away from home, so that the last—and fatal—dose was actually taken twenty-four hours later than had been anticipated by the murderer; and it is owing to that delay that the final proof—the last link of the chain—is now in my hands.”
Amid breathless excitement, he held out three thin strips of paper.
“A letter in the murderer’s own hand-writing, mes amis! Had it been a little clearer in its terms, it is possible that Mrs. Inglethorp, warned in time, would have escaped. As it was, she realized her danger, but not the manner of it.”
In the deathly silence, Poirot pieced together the slips of paper and, clearing his throat, read:
“‘Dearest Evelyn:
‘You will be anxious at hearing nothing. It is all right—only it will be to-night instead of last night. You understand. There’s a good time coming once the old woman is dead and out of the way. No one can possibly bring home the crime to me. That idea of yours about the bromides was a stroke of genius! But we must be very circumspect. A false step——’
“Here, my friends, the letter breaks off. Doubtless the writer was interrupted; but there can be no question as to his identity. We all know this hand-writing and——”
A howl that