I was to have a further proof that day of the success of Poirot's tactics. That challenge of his had been a subtle touch born of his knowledge of human nature. A mixture of fear and guilt had wrung the truth from Mrs Ackroyd. She was the first to react.

"No, to his own house."

That afternoon when I returned from seeing my patients, Caroline told me that Geoffrey Raymond had just left.

"The side window," said Caroline briefly.

"I tried to make him wait," said Caroline, "but he said he would call back at The Larches in half an hour, and went away down the village. A great pity, because M. Poirot came in practically the minute after he left."

"It was M. Poirot he wanted to see," she said. "He'd just come from the Larches. Mr. Poirot was out. Mr Raymond thought that he might be here, or that you might know where he was."

"I haven't the least idea."

"Came in here?"

Caroline was hovering by my elbow.

"How do you know?"

It seemed to me that we had now exhausted the topic. Caroline thought otherwise.

"Did he want to see me?" I asked, as I hung up my coat in the hall.

"To The Larches, of course."

"My dear Caroline," I said, "what for?"

"Why can't Annie go?" I asked coldly.

"She's doing some mending. I can't spare her." Caroline and I looked at each other.

"Stuff and nonsense, James," said my sister. "You want to know just as much as I do. You're not so honest, that's all. You always have to pretend."

"Really, Caroline," I said, and retired into my surgery.

"Curiosity is not my besetting sin," I remarked coldly. "I can exist comfortably without knowing exactly what my neighbours are doing and thinking."

"Across where?"

"Very well," I said, rising. "But if I take the beastly thing, I shall just leave it at the door. You understand that?"

Ten minutes later Caroline tapped at the door and entered. In her hand she held what seemed to be a pot of jam.

"I wonder, James," she said, "if you would mind taking this pot of medlar jelly across to M. Poirot? I promised it to him. He has never tasted any home-made medlar jelly."

"Aren't you going across?"

"Mr Raymond wanted to see him very particularly s; ^ Caroline. "You might hear what it's all about."

I raised my eyebrows.

"If you do happen to see M. Poirot," she said, as I opened the front door, "you might tell him about the boots."

My sister raised her eyebrows. "Naturally," she said. "Who suggested you should do anything else?"

The honours were with Caroline.

It was a most subtle parting shot. I wanted dreadfully to understand the enigma of the boots. When the old lady with the Breton cap opened the door to me, I found myself asking if M. Poirot was in, quite automatically.

Poirot sprang up to meet me, with every appearance of pleasure.

"Sit down, my good friend," he said. "The big chair? This small one? The room is not too hot, no?"

I thought it was stifling, but refrained from saying so. The windows were closed, and a large fire burned in the grate.

"The English people, they have a mania for the fresh air," declared Poirot. "The big air, it is all very well outside, where " belongs. Why admit it to the house? But let us not discuss ^ch banalities. You have something for me, yes?"

"Two things," I said. "First -- this -- from my sister." I handed over the pot of medlar jelly.

"Information -- of a kind." And I told him of my interview with Mrs Ackroyd. He listened with interest, but not much excitement.

"How kind of Mademoiselle Caroline. She has remembered her promise. And the second thing?"

"It clears the ground," he said thoughtfully. "And it has a certain value as confirming the evidence of the housekeeper. She said, you remember, that she found the silver table lid open and closed it down in passing."

"What about her statement that she went into the drawing-room to see if the flowers were fresh?"

"Ah! we never took that very seriously, did we, my friend? It was patently an excuse, trumped up in a hurry, by a woman who felt it urgent to explain her presence -- which, by the way, you would probably never have thought of questioning. I considered it possible that her agitation might arise from the fact that she had been tampering with the silver table, but I think now that we must look for another cause."

"You think she went to meet someone?"

"Yes," I said. "Whom did she go out to meet? And why?"

"Not at all," I said. "When the professional part of the conversation was over, we talked for a few minutes about poisons, and the ease or difficulty of detecting them, and about drug-taking and drug-takers."

"Ah!" said Poirot regretfully. "That is a pity." And he seemed quite crestfallen.

"With special reference to cocaine?" asked Poirot.

"By the way," I said, "I've got a message for you from my sister. Ralph Paton's boots were black, not brown." I was watching him closely as I gave the message, and I fancied that I saw a momentary flicker of discomposure. If so, it passed almost immediately.

"How did you know?" I asked, somewhat surprised.

He entered into no explanations, but at once started a new subject of conversation.

"So do I," he said thoughtfully.

"Absolutely."

There was a pause.

"She is absolutely positive they are not brown?"

"I do." Poirot nodded.

"The housekeeper. Miss Russell, who came to consult you on that Friday morning -- is it indiscreet to ask what passed at the interview -- apart from the medical details, I mean?"

He came in fresh and debonair as ever, and greeted us both.

"How are you, doctor? M. Poirot, this is the second time I've been here this morning. I was anxious to catch you."

"That is what put cocaine into her head, my friend," he said.

For answer, the little man rose and crossed the room to where newspapers were filed. He brought me a copy of the Daily Budget, dated Friday, 16th September, and showed me an article dealing with the smuggling of cocaine. It was a somewhat lurid article, written with an eye to picturesque effect.

"Perhaps I'd better be off," I suggested rather awkwardly.

"Oh, it's of no consequence, really. But, as a matter of fact, my conscience has been pricking me ever since yesterday afternoon. You accused us all of keeping back something, M. Poirot. I plead guilty. I've had something up my sleeve."

I would have catechized him further, for I did not quite understand his meaning, but at that moment the door opened and Geoffrey Raymond was announced.

"Not on my account, doctor. No, it's just this," he went on, seating himself at a wave of invitation from Poirot, "I've got a confession to make."

"En verite?" said Poirot, with an air of polite interest.

"You know how it is. Suspicious-looking policemen -- don't like to admit you were hard up for money -- think it will look bad to them. But I was a fool, really, because Blunt and I were in the billiard room from a quarter to ten onwards, so I've got a watertight alibi and nothing to fear. Still, when you thundered out that stuff about concealing things, I felt a nasty prick of conscience, and I thought I'd like to get it off my mind." He got up again and stood smiling at us.

"And what is that, M. Raymond?"

"As I say, it's nothing of consequence- just this. I was in debt -- badly, and that legacy came in the nick of time. Five hundred pounds puts me on my feet again with a little to spare." He smiled at us both with that engaging frankness that made him such a likeable youngster.

"You are a very wise young man," said Poirot, nodding at him with approval. "See you, when I know that anyone is hiding things from me, I suspect that the thing hidden may be something very bad indeed. You have done well."

"I'm glad I'm cleared from suspicion," laughed Raymond Til be off now."

"So that is that," I remarked, as the door closed behind the young secretary.

"As for that," remarked Poirot nonchalantly, "there is a saying, is there not, that Englishmen conceal only one thing their love? And Major Blunt, I should say, is not good at concealments."

"Yes," agreed Poirot. "A mere bagatelle -- but if he had not been in the billiard room -- who knows? After all, many crimes have been committed for the sake of less than five hundred pounds. It all depends on what sum is sufficient to break a man. A question of relativity, is it not so? Have you reflected, my friend, that many people in that house stood to benefit by Mr Ackroyd's death? Mrs Ackroyd, Miss Flora, young Mr Raymond, the housekeeper. Miss Russell. Only one, in fact, does not. Major Blunt." His tone in uttering that name was so peculiar that I looked up, puzzled.

"Two of the people I accused have given me the truth."

"I don't understand you," I said.

"You think Major Blunt has something to conceal also?"

"Sometimes," I said, "I wonder if we haven't rather jumped to conclusions on one point."

"We've assumed that the blackmailer of Mrs Ferrars is necessarily the murderer of Mr Ackroyd. Mightn't we be mistaken?"

"What is that?"

Poirot nodded energetically. "Very good. Very good indeed. I wondered if that idea would come to you. Of course it is possible. But we must remember one point. The letter disappeared. Still, that, as you say, may not necessarily mean that the murderer took it. When you first found the body, Parker may have abstracted the letter unnoticed by you."

"Parker might have taken the letter," I admitted. "It wasn't till later that I noticed it was gone."

"Parker?"

"How much later? After Blunt and Raymond were in the room, or before?"

"Yes, Parker. I always come back to Parker -- not as the murderer -- no, he did not commit the murder; but who is more suitable than he as the mysterious scoundrel who terrorized Mrs Ferrars? He may have got his information about Mr Ferrars's death from one of the King's Paddock servants. At any rate, he is more likely to have come upon it than a casual guest such as Blunt, for instance."

I acquiesced, and we set out at once. Poirot asked to see Miss Ackroyd, and presently Flora came to us.

"I can't remember," I said slowly. "I think it was before no, afterwards. Yes, I'm almost sure it was afterwards."

"You rang, sir?"

"That widens the field to three," said Poirot thoughtfully. "But Parker is the most likely. It is in my mind to try a little experiment with Parker. How say you, my friend, will you accompany me to Fernly?"

"Yes, my good Parker. I have in mind a little experiment. I have placed Major Blunt on the terrace outside the study window. I want to see if anyone there could have heard the voices of Miss Ackroyd and yourself in the lobby that night. I want to enact that little scene over again. Perhaps you would fetch the tray or whatever it was you were carrying?"

"Mademoiselle Flora," said Poirot, "I have to confide in you a little secret. I am not yet satisfied of the innocence of Parker. I propose to make a little experiment with your assistance. I want to reconstruct some of his actions on that night. But we must think of something to tell him -- ah! I have it. I wish to satisfy myself as to whether voices in the little lobby could have been heard outside on the terrace. Now, ring for Parker, if you will be so good." I did so, and presently the butler appeared, suave as ever.

Parker vanished, and we repaired to the lobby outside the study door. Presently we heard a chink in the outer hall, and Parker appeared in the doorway carrying a tray with a siphon, a decanter of whisky, and two glasses on it.

"A foreign custom, sir," said Parker. "Reconstruction of the crime they call it, do they not?" He was quite imperturbable as he stood there politely waiting on Poirot's orders.

"One moment," cried Poirot, raising his hand and seemingly very excited. "We must have everything in order. Just as it occurred. It is a little method of mine."

"Ah! he knows something, the good Parker," cried Poirot. "He has read of these things. Now, I beg you, let us have everything of the most exact. You came from the outer hall -- so. Mademoiselle was -- where?"

"Quite right, sir," said Parker.

"Here," said Flora, taking up her stand just outside the study door.

"Then allez," said Poirot. "Play me the little comedy."

"I had just closed the door," continued Flora.

"Yes, miss," agreed Parker. "Your hand was still on the handle as it is now."

Flora stood with her hand on the door handle, and Parker came stepping through the door from the hall, bearing the tray.

"To the best of my recollection, Miss Flora," said Parker, "but I fancy you used the word evening instead of night." Then, raising his voice in a somewhat theatrical fashion: "Very good, miss. Shall I lock up as usual?"

"Is that right?" she added in an undertone.

"Admirable," declared the little man, rubbing his hands. "By the way, Parker, are you sure there were two glasses on the tray that evening? Who was the second one for?"

"Yes, please." Parker retired through the door. Flora followed him, and started to ascend the main staircase.

Parker withdrew, dignified to the last.

He stopped just inside the door. Flora spoke. "Oh! Parker. Mr Ackroyd doesn't want to be disturbed again tonight."

"Nothing. I thank you."

Poirot stood in the middle of the hall frowning.

"Is that enough?" she asked over her shoulder.

"I always bring two glasses, sir," said Parker. "Is there anything further?"

A few minutes later saw us retracing our steps to the village.

Poirot took her hand and patted it. "Put it this way," he said. "I am always interested to see if people will speak the truth."

"One must say something," he remarked. "That particular question did as well as any other."

"And did Parker speak the truth?"

Poirot shrugged his shoulders.

"What was the point of that question about the glasses?" I asked curiously.

Flora came down and joined us. "Has your experiment been successful?" she asked. "I don't quite understand, you know --"

Poirot smiled admiringly at her. "It is not necessary that you should," he said. "But tell me, were there indeed two glasses on Parker's tray that night?"

"I rather think he did," said Poirot thoughtfully.

Flora wrinkled her brows a minute. "I really can't remember," she said. "I think there were. Is -- is that the object of your experiment?"

I stared at him.

"At any rate, my friend," he said seriously, "I know now something I wanted to know. Let us leave it at that."