‘No? I made sure that he had been having a stormy altercation with M. de Saint Alard.’
‘Why should he?’
‘C’est évident!’ The doctor shrugged his shoulders. ‘Was not M. de Saint Alard a Catholic of the most fanatical? Their friendship was being ruined by this question of church and state. Not a day passed without discussions. To M. de Saint Alard, Déroulard appeared almost as Antichrist.’
This was unexpected, and gave me food for thought.
‘One more question, Doctor: would it be possible to introduce a fatal dose of poison into a chocolate?’
‘It would be possible, I suppose,’ said the doctor slowly. ‘Pure prussic acid would meet the case if there were no chance of evaporation, and a tiny globule of anything might be swallowed unnoticed—but it does not seem a very likely supposition. A chocolate full of morphine or strychnine—’ He made a wry face. ‘You comprehend, M. Poirot—one bite would be enough! The unwary one would not stand upon ceremony.’
‘Thank you, M. le Docteur.’
I withdrew. Next I made inquiries of the chemists, especially those in the neighbourhood of the Avenue Louise. It is good to be of the police. I got the information I wanted without any trouble. Only in one case could I hear of any poison having been supplied to the house in question. This was some eye drops of atropine sulphate for Madame Déroulard. Atropine is a potent poison, and for the moment I was elated, but the symptoms of atropine poisoning are closely allied to those of ptomaine, and bear no resemblance to those I was studying. Besides, the prescription was an old one. Madame Déroulard had suffered from cataract in both eyes for many years.
I was turning away discouraged when the chemist’s voice called me back.
‘Un moment, M. Poirot. I remember, the girl who brought that prescription, she said something about having to go on to the English chemist. You might try there.’
I did. Once more enforcing my official status, I got the information I wanted. On the day before M. Déroulard’s death they had made up a prescription for Mr John Wilson. Not that there was any making up about it. They were simply little tablets of trinitrine. I asked if I might see some. He showed me them, and my heart beat faster—for the tiny tablets were of chocolate.
‘Is it a poison?’ I asked.
‘No, monsieur.’
‘Can you describe to me its effect?’
‘It lowers the blood-pressure. It is given for some forms of heart trouble—angina pectoris for instance. It relieves the arterial tension. In arteriosclerosis—’
I interrupted him. ‘Ma foi! This rigmarole says nothing to me. Does it cause the face to flush?’
‘Certainly it does.’
‘And supposing I ate ten—twenty of your little tablets, what then?’
‘I should not advise you to attempt it,’ he replied drily.
‘And yet you say it is not poison?’
‘There are many things not called poison which can kill a man,’ he replied as before.
I left the shop elated. At last, things had begun to march!
I now knew that John Wilson had the means for the crime—but what about the motive? He had come to Belgium on business, and had asked M. Déroulard, whom he knew slightly, to put him up. There was apparently no way in which Déroulard’s death could benefit him. Moreover, I discovered by inquiries in England that he had suffered for some years from that painful form of heart disease known as angina. Therefore he had a genuine right to have those tablets in his possession. Nevertheless, I was convinced that someone had gone to the chocolate box, opening the full one first by mistake, and had abstracted the contents of the last chocolate, cramming in instead as many little trinitrine tablets as it would hold. The chocolates were large ones. Between twenty or thirty tablets, I felt sure, could have been inserted. But who had done this?
There were two guests in the house. John Wilson had the means. Saint Alard had the motive. Remember, he was a fanatic, and there is no fanatic like a religious fanatic. Could he, by any means, have got hold of John Wilson’s trinitrine?
Another little idea came to me. Ah, you smile at my little ideas! Why had Wilson run out of trinitrine? Surely he would bring an adequate supply from England. I called once more at the house in the Avenue Louise. Wilson was out, but I saw the girl who did his room, Félicie. I demanded of her immediately whether it was not true that M. Wilson had lost a bottle from his washstand some little time ago. The girl responded eagerly. It was quite true. She, Félicie, had been blamed for it. The English gentleman had evidently thought that she had broken it, and did not like to say so. Whereas she had never even touched it. Without doubt it was Jeannette always nosing round where she had no business to be—
I calmed the flow of words, and took my leave. I knew now all that I wanted to know. It remained for me to prove my case. That, I felt, would not be easy. I might be sure that Saint Alard had removed the bottle of trinitrine from John Wilson’s washstand, but to convince others, I would have to produce evidence. And I had none to produce!
Never mind. I knew—that was the great thing. You remember our difficulty in the Styles case, Hastings? There again, I knew—but it took me a long time to find the last link which made my chain of evidence against the murderer complete.
I asked for an interview with Mademoiselle Mesnard. She came at once. I demanded of her the address of M. de Saint Alard. A look of trouble came over her face.
‘Why do you want it, monsieur?’
‘Mademoiselle, it is necessary.’
She seemed doubtful—troubled.
‘He can tell you nothing. He is a man whose thoughts are not in this world. He hardly notices what goes on around him.’
‘Possibly, mademoiselle. Nevertheless, he was an old friend of M. Déroulard’s. There may be things he can tell me—things of the
