"Yes. There was a school of treatment at the time which was very popular and which my father believed in. That school's belief was that after sufficient treatment, lasting sometimes quite a long time, a year or longer, people could resume a normal everyday life, and it was to their advantage to do so. They could be returned to live at home and with a suitable amount of attention, both medical and from those, usually near relatives, who were with them and could observe them living a normal life, everything would go well. This, I may say, did meet with success at first in many cases, but later there was a difference. Several cases had most unfortunate results. Patients who appeared to be cured came home to their natural surroundings, to a family, a husband, their mothers and fathers, and slowly relapsed, so that very often tragedies or near-tragedies occurred. One case my father was bitterly disappointed in-also a very important case in his knowledge- was a woman who came back to live with the same friend she lived with before. All seemed to be going happily, but after about five or six months she sent urgently for a doctor and when he came^said, "I must take you upstairs because you will be angry at what I have done, and you will have to send for the police, I am afraid. I know that must happen. But you see, I was commanded to do this, I saw the Devil looking out of Hilda's eyes. I saw the Devil there so I knew what I had to do.
I knew I had to kill her.' The woman was lying dead in a chair, strangled, and after her death her eyes had been attacked.
The killer died in a mental home with never any feeling about her crime except that it had been a necessary command laid upon her because it was her duty to destroy the Devil." Poirot shook his head sadly. \ The doctor went on: "Yes. Well, I consider that in a mild way Dorothea Preston-Grey suffered from a form of mental disorder that was dangerous and that she could only be considered safe if she lived under supervision. This was not generally accepted, I may say, at the time, and my father did consider it most inadvisable. After she had been committed once more to a very pleasant nursing home a very good treatment was given. And again, after a period of years she appeared to be completely sane, left the establishment, lived an ordinary life with a very pleasant nurse more or less in charge of her, though considered in the household as a lady's maid. She went about, made friends and sooner or later went abroad." "To India," said Poirot.
"Yes. I see you've been correctly informed. She went to India to stay with her twin sister." "And there another tragedy happened?" "Yes. A child of a neighbor was attacked. It was thought at first by an ayah, and afterwards I believe one of the native servants, a bearer, was suspected. But there again there seemed no doubt that Mrs. Jarrow had, for one of those mental reasons known only to her, been guilty of the attack. There was no definite evidence, I understand, which could be brought against her. I think General-I forget his name now-" "Ravenscroft?" said Poirot.
"Yes, yes, General Ravenscroft agreed to arrange for her to go back to England and again undergo medical treatment. Is that what you wanted to know?" "Yes," said Poirot, "that is what I have partly heard already, but mainly, I may say, by hearsay, which is not dependable.
What I want to ask you was, this was a case concerned with identical twins. What about the other twin? Margaret PrestonGrey.
Afterwards the wife of General Ravenscroft. Was she likely to be affected by the same malady?" "There was never any medical case about her. She was perfectly sane. My father was interested, visited her once or twice and talked to her because he had so often seen cases of almost identical illnesses or mental disturbances happen between identical twins who had started life very devoted to each other." "Only started life, you said?" "Yes. On certain occasions a state of animosity can arise between identical twins. It follows on a first keen protective love one for the other, but it can degenerate into something which is nearer hatred, if there is some emotional strain that could trigger it off or could arouse it, or any emotional crisis to account for animosity arising between two sisters.
"I think there might have been that here. General Ravenscroft as a young subaltern or captain or whatever he was, fell deeply in love, I think, with Dorothea Preston-Grey, who was a very beautiful girl. Actually the more beautiful of the two.