Agatha Christie: The Mysterious Affair at Styles

CHAPTER 12. THE LAST LINK (continued)

"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----"