“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.