“Cheer up, John!” I said soothingly. “It can’t last for ever.”

“Can’t it, though? It can last long enough for us never to be able to hold up our heads again.”

“No, no, you’re getting morbid on the subject.”

“Enough to make a man morbid, to be stalked by beastly journalists and stared at by gaping moon-faced idiots, wherever he goes! But there’s worse than that.”

“What?”

John lowered his voice:

“Have you ever thought, Hastings—it’s a nightmare to me—who did it? I can’t help feeling sometimes it must have been an accident. Because—because—who could have done it? Now Inglethorp’s out of the way, there’s no one else; no one, I mean, except—one of us.”

Yes, indeed, that was nightmare enough for any man! One of us? Yes, surely it must be so, unless——-

A new idea suggested itself to my mind. Rapidly, I considered it. The light increased. Poirot’s mysterious doings, his hints—they all fitted in. Fool that I was not to have thought of this possibility before, and what a relief for us all.

“No, John,” I said, “it isn’t one of us. How could it be?”

“I know, but, still, who else is there?”

“Can’t you guess?”

“No.”

I looked cautiously round, and lowered my voice.

“Dr. Bauerstein!” I whispered.

“Impossible!”

“Not at all.”

“But what earthly interest could he have in my mother’s death?”

“That I don’t see,” I confessed, “but I’ll tell you this: Poirot thinks so.”

“Poirot? Does he? How do you know?”

I told him of Poirot’s intense excitement on hearing that Dr. Bauerstein had been at Styles on the fatal night, and added:

“He said twice: ‘That alters everything.’ And I’ve been thinking. You know Inglethorp said he had put down the coffee in the hall? Well, it was just then that Bauerstein arrived. Isn’t it possible that, as Inglethorp brought him through the hall, the doctor dropped something into the coffee in passing?”

“H’m,” said John. “It would have been very risky.”

“Yes, but it was possible.”

“And then, how could he know it was her coffee? No, old fellow, I don’t think that will wash.”

But I had remembered something else.

“You’re quite right. That wasn’t how it was done. Listen.” And I then told him of the cocoa sample which Poirot had taken to be analysed.

John interrupted just as I had done.

“But, look here, Bauerstein had had it analysed already?”

“Yes, yes, that’s the point. I didn’t see it either until now. Don’t you understand? Bauerstein had it analysed—that’s just it! If Bauerstein’s the murderer, nothing could be simpler than for him to substitute some ordinary cocoa for his sample, and send that to be tested. And of course they would find no strychnine! But no one would dream of suspecting Bauerstein, or think of taking another sample—except Poirot,” I added, with belated recognition.

“Yes, but what about the bitter taste that cocoa won’t disguise?”

“Well, we’ve only his word for that. And there are other possibilities. He’s admittedly one of the world’s greatest toxicologists——”

“One of the world’s greatest what? Say it again.”

“He knows more about poisons than almost anybody,” I explained. “Well, my idea is, that perhaps he’s found some way of making strychnine tasteless. Or it may not have been strychnine at all, but some obscure drug no one has ever heard of, which produces much the same symptoms.”

“H’m, yes, that might be,” said John. “But look here, how could he have got at the cocoa? That wasn’t downstairs?”

“No, it wasn’t,” I admitted reluctantly.

And then, suddenly, a dreadful possibility flashed through my mind. I hoped and prayed it would not occur to John also. I glanced sideways at him. He was frowning perplexedly, and I drew a deep breath of relief, for the terrible thought that had flashed across my mind was this: that Dr. Bauerstein might have had an accomplice.

Yet surely it could not be! Surely no woman as beautiful as Mary Cavendish could be a murderess. Yet beautiful women had been known to poison.

And suddenly I remembered that first conversation at tea on the day of my arrival, and the gleam in her eyes as she had said that poison was a woman’s weapon. How agitated she had been on that fatal Tuesday evening! Had Mrs. Inglethorp discovered something between her and Bauerstein, and threatened to tell her husband? Was it to stop that denunciation that the crime had been committed?

Then I remembered that enigmatical conversation between Poirot and Evelyn Howard. Was this what they had meant? Was this the monstrous possibility that Evelyn had tried not to believe?

Yes, it all fitted in.

No wonder Miss Howard had suggested “hushing it up.” Now I understood that unfinished sentence of hers: “Emily herself——” And in my heart I agreed with her. Would not Mrs. Inglethorp have preferred to go unavenged rather than have such terrible dishonour fall upon the name of Cavendish.

“There’s another thing,” said John suddenly, and the unexpected sound of his voice made me start guiltily. “Something which makes me doubt if what you say can be true.”

“What’s that?” I asked, thankful that he had gone away from the subject of how the poison could have been introduced into the cocoa.

“Why, the fact that Bauerstein demanded a post-mortem. He needn’t have done so. Little Wilkins would have been quite content to let it go at heart disease.”

“Yes,” I said doubtfully. “But we don’t know. Perhaps he thought it safer in the long run. Someone might have talked afterwards. Then the Home Office might have ordered exhumation. The whole thing would have come out, then, and he would have been in an awkward position, for no one would have believed that a man of his reputation could have been deceived into calling it heart disease.”

“Yes, that’s possible,” admitted John. “Still,” he added, “I’m blest if I can see what his motive could have been.”

I trembled.

“Look here,” I said, “I may be altogether wrong. And, remember, all this is in confidence.”

“Oh, of course—that goes without saying.”