Poirot said: "You did not leave the marquee again until your mother-in-law was found dead? That is what you have just said. That, Mrs. Boynton, was one of the points I found curious about this case."

"What do you mean?"

"It is here on my list. Point 9. At half-past six, when dinner was ready, a servant was dispatched to announce the fact to Mrs. Boynton."

Raymond said: "I don't understand."

Carol said: "No more do I."

Poirot looked from one to the other of them. "You do not, eh? 'A servant was sent'. Why a servant? Were you not, all of you, most assiduous in your attendance on the old lady as a general rule? Did not one or another of you always escort her to meals? She was infirm. It was difficult for her to rise from a chair without assistance. Always one or another of you was at her elbow. I suggest then, that on dinner being announced, the natural thing would have been for one or another of her family to go out and help her. But not one of you offered to do so. You all sat there, paralyzed, watching each other, wondering perhaps, why no one went."

Nadine said sharply: "All this is absurd, M. Poirot! We were all tired that evening. We ought to have gone, I admit, but—on that evening—we just didn't!"

"Precisely—precisely—on that particular evening! You, Madame, did perhaps more waiting on her than anyone else. It was one of the duties that you accepted mechanically. But that evening you did not offer to go out to help her in. Why? That is what I asked myself—why? And I tell you my answer. Because you knew quite well that she was dead. . . ."

"No, no, do not interrupt me, Madame." He raised an impassioned hand. "You will now listen to me—Hereule Poirot! There were witnesses to your conversation with your mother-in-law. Witnesses who could see but who could not hear! Lady Westholme and Miss Pierce were a long way off. They saw you apparently having a conversation with your mother-in-law, but what actual evidence is there of what occurred? I will propound to you instead a little theory. You have brains, Madame. If in your quiet, unhurried fashion you have decided on—shall we say the elimination of your husband's mother?—you will carry it out with intelligence and with due preparation. You have access to Dr. Gerard's tent during his absence on the morning excursion. You are fairly sure that you will find a suitable drug. Your nursing training helps you there. You choose digitoxin—the same kind of drug that the old lady is taking. You also take his hypodermic syringe since, to your annoyance, your own has disappeared. You hope to replace the latter before the doctor notices its absence."