e the coffee-cups!"

"My dear Poirot! What on earth is the good of that, now that we know
about the coco?"

"Oh, la la! That miserable coco!" cried Poirot flippantly.

He laughed with apparent enjoyment, raising his arms to heaven in mock
despair, in what I could not but consider the worst possible taste.

"And, anyway," I said, with increasing coldness, "as Mrs. Inglethorp
took her coffee upstairs with her, I do not see what you expect to
find, unless you consider it likely that we shall discover a packet of
strychnine on the coffee tray!"

Poirot was sobered at once.

"Come, come, my friend," he said, slipping his arms through mine. "Ne
vous fachez pas! Allow me to interest myself in my coffee-cups, and I
will respect your coco. There! Is it a bargain?"

He was so quaintly humorous that I was forced to laugh; and we went
together to the drawing-room, where the coffee-cups and tray remained
undisturbed as we had left them.

Poirot made me recapitulate the scene of the night before, listening
very carefully, and verifying the position of the various cups.

"So Mrs. Cavendish stood by the tray--and poured out. Yes. Then she came
across to the window where you sat with Mademoiselle Cynthia. Yes. Here
are the three cups. And the cup on the mantel-piece, half drunk, that
would be Mr. Lawrence Cavendish's. And the one on the tray?"

"John Cavendish's. I saw him put it down there."

"Good. One, two, three, four, five--but where, then, is the cup of Mr.
Inglethorp?"

"He does not take coffee."

"Then all are accounted for. One moment, my friend."

With infinite care, he took a drop or two from the grounds in each cup,
sealing them up in separate test tubes, tasting each in turn as he did
so. His physiognomy underwent a curious change. An expression gathered
there that I can only describe as half puzzled, and half relieved.

"Bien!" he said at last. "It is evident! I had an idea--but clearly I
was mistaken. Yes, altogether I was mistaken. Yet it is strange. But no
matter!"

And, with a characteristic shrug, he dismissed whatever it was that was
worrying him from his mind. I could have told him from the beginning
that this obsession of his over the coffee was bound to end in a blind
alley, but I restrained my tongue. After all, though he was old, Poirot
had been a great man in his day.

"Breakfast is ready," said John Cavendish, coming in from the hall. "You
will breakfast with us, Monsieur Poirot?"

Poiro