“There remained his sister Theresa, Dr.
Tanios, Mrs. Tanios and Dr. Donaldson, who I discovered to have been dining in the house on the evening of the dog’s ball incident.
“At this point I had very little to help me.
I had to fall back upon the psychology of the crime and the personality of the murderer!
Both crimes had roughly the same outline. They were both simple. They were cunning, and carried out with efficiency. They required a certain amount of knowledge but not a great deal. The facts about phosphorus poisoning are easily learned, and the stuff itself, as I say, is quite easily obtained, especially abroad.
“I considered first the two men. Both of them were doctors, and both were clever men. Either of them might have thought of phosphorus and its suitability in this particular case, but the incident of the dog’s ball did not seem to fit a masculine mind. The incident of the ball seemed to me essentially a woman’s idea.
“I considered first of all Theresa Arundell.
She had certain potentialities. She was bold, ruthless, and not overscrupulous. She had led a selfish and greedy life. She had always had everything she wanted and she had reached a point where she was desperate for money–both for herself and for the man she loved. Her manner, also, showed plainly that she knew her aunt had been murdered.
“There was an interesting little passage between her and her brother. I conceived the idea that each suspected the other of the crime. Charles endeavoured to make her say that she knew of the existence of the new will. Why? Clearly because if she knew of it she could not be suspected of the murder. She, on the other hand, clearly did not believe Charles’s statement that Miss Arundell had shown it to him! She regarded it as a singularly clumsy attempt on his part to divert suspicion from himself.
“There was another significant point.
Charles displayed a reluctance to use the word arsenic. Later I found that he had questioned the old gardener at length upon the strength of some weed-killer. It was clear what had been in his mind.” Charles Arundell shifted his position a little.
“I thought of it,” he said. “But–well, I suppose I hadn’t got the nerve.” Poirot nodded at him.
“Precisely, it is not in your psychology. Your crimes will always be the crimes of weakness.
To steal, to forge–yes, it is the easiest way–but to kill–no! To kill one needs the type of mind that can be obsessed by an idea.” He resumed his lecturing manner.
“Theresa Arundell, I decided, had quite sufficient strength of mind to carry such a design through, but there were other facts to take into consideration. She had never been thwarted, she had lived fully and selfishly–but that type of person is not the type that kills–except perhaps in sudden anger.
And yet–I felt sure–it was Theresa Arundell who had taken the weed-killer from the tin.” Theresa spoke suddenly: “I’ll tell you the truth. I thought of it. I actually took some weed-killer from a tin down at Littlegreen House. But I couldn’t do it! I’m too fond of living–of being alive–I couldn’t do that to any one–take life from them…. I may be bad and selfish, but there are things I can’t do! I couldn’t kill a living, breathing, human creature!” Poirot nodded.
“No, that is true. And you are not as bad as you paint yourself, mademoiselle. You are only young–and reckless.” He went on: “There remained Mrs. Tanios. As soon as I saw her I realized that she was afraid. She saw that I realized that and she very quickly made capital out of that momentary betrayal.
She gave a very convincing portrait of a woman who is afraid for her husband. A little later she changed her tactics. It was very cleverly done–but the change did not deceive me. A woman can be afraid for her husband or she can be afraid of her husband–but she can hardly be both. Mrs.
Tanios decided on the latter role–and she played her part cleverly–even to coming out after me into the hall of the hotel and pretending that there was something she wanted to tell me. When her husband followed her as she knew he would, she pretended that she could not speak before him.