"Ah, why indeed?" said Poirot, calming down. "If he were arrested, he probably would speak, but I do not want it to come to that. I must make him see the gravity of his position. There is, of course, something discreditable behind his silence. If he did not murder his wife, he is, nevertheless, a scoundrel, and has something of his own to conceal, quite apart from the murder."
"What can it be?" I mused, won over to Poirot's views for the moment, although still retaining a faint conviction that the obvious deduction was the correct one.
"Can you not guess?" asked Poirot, smiling.
"No, can you?"
"Oh, yes, I had a little idea sometime ago--and it has turned out to be correct."
"You never told me," I said reproachfully.
Poirot spread out his hands apologetically.
"Pardon me, mon ami, you were not precisely sympathique." He turned to me earnestly. "Tell me--you see now that he must not be arrested?"
"Perhaps," I said doubtfully, for I was really quite indifferent to the fate of Alfred Inglethorp, and thought that a good fright would do him no harm.
Poirot, who was watching me intently, gave a sigh.
"Come, my friend," he said, changing the subject, "apart from Mr. Inglethorp, how did the evidence at the inquest strike you?"
"Oh, pretty much what I expected."
"Did nothing strike you as peculiar about it?"
My thoughts flew to Mary Cavendish, and I hedged: "In what way?"
"Well, Mr. Lawrence Cavendish's evidence for instance?"
I was relieved.
"Oh, Lawrence! No, I don't think so. He's always a nervous chap."
"His suggestion that his mother might have been poisoned accidentally by means of the tonic she was taking, that did not strike you as strange--hein?"
"No, I can't say it did. The doctors ridiculed it of course. But it was quite a natural suggestion for a layman to make."
"But Monsieur Lawrence is not a layman. You told me yourself that he had started by studying medicine, and that he had taken his degree."
"Yes, that's true. I never thought of that." I was rather startled. "It is odd."
Poirot nodded.
"From the first, his behaviour has been peculiar. Of all the household, he alone would be likely to recognize the symptoms of strychnine poisoning, and yet we find him the only member of the family to uphold strenuously the theory of death from natural causes. If it had been Monsieur John, I could have understood it. He has no technical knowledge, and is by nature unimaginative. But Monsieur Lawrence--no! And now, to-day, he puts forward a suggestion that he himself must have known was ridiculous. There is food for thought in this, mon ami!"