"Have I not told you at least thirty-six times that it is useless to conceal things from Hercule Poirot?" he demanded. "That in such a case he finds out?" He turned to the others.

It was a very uncomfortable minute for me. I hardly took in what happened next, but there were exclamations and cries of surprise! When I was sufficiently master of myself to be able to realize what was going on, Ralph Paton was standing by his wife, her hand in his, and he was smiling across the room at me.

Poirot, too, was smiling, and at the same time shaking an eloquent finger at me.

"One day, you remember, we held a little seance about a table -- just the six of us. I accused the other five persons present of concealing something from me. Four of them gave up their secret. Dr Sheppard did not give up his. But all along I have had my suspicions. Dr Sheppard went to the Three Boars that night hoping to find Ralph. He did not find him there; but supposing, I said to myself, that he met him in the street on his way home? Dr Sheppard was a friend of Captain Paton's, and he had come straight from the scene of the crime. He must know that things looked very black against him. Perhaps he knew more than the general public did --"

I hesitated, and Ralph filled up the gap. "To do a bunk," he said graphically. "You see, Ursula left me to go back to the house. I thought it possible that she might have attempted to have another interview with my stepfather. He had already been very rude to her that afternoon. It occurred to me that he might have so insulted her -- in such an unforgivable manner -- that without knowing what she was doing ". He stopped. Ursula released her hand from his, and stepped back.

"I did," I said ruefully. "I suppose I might as well make a clean breast of things now. I went to see Ralph that afternoon. At first he refused to take me into his confidence, but later he told me about his marriage, and the hole he was in. As soon as the murder was discovered, I realized that once the facts were known, suspicion could not fail to attach to Ralph -- or, if not to him, to the girl he loved. That night I put the facts plainly before him. The thought of having possibly to give evidence which might incriminate his wife made him resolve at all costs to -- to --"

"Where?" asked Raymond. "In his own house?"

"You thought that, Ralph! You actually thought that I might have done it?"

"Ah, no, indeed," said Poirot. "You should ask yourself the question that I did. If the good doctor is concealing the young man, what place would he choose? It must necessarily be somewhere near at hand. I think ofCranchester. A hotel? No. Lodgings? Even more emphatically, no. Where, then? Ah! I have it. A nursing home. A home for the mentally unfit. I test my theory. I invent a nephew with mental trouble. I consult Mademoiselle Sheppard as to suitable homes. She gives me the names of two near Cranchester to which her brother has sent patients. I make inquiries. Yes, at one of them a patient was brought there by the doctor himself early on Saturday morning. That patient, though known by another name, I had no difficulty in identifying as Captain Paton. After certain necessary formalities, I was allowed to bring him away. He arrived at my house in the early hours of yesterday morning."

"Let us get back to the culpable conduct of Dr Sheppard," said Poirot drily. "Dr Sheppard consented to do what he could to help him. He was successful in hiding Captain Paton from the police."

"Caroline's Home Office expert," I murmured. "And to think I never guessed!"

I looked at him ruefully.

"Dr Sheppard has been very loyal," said Ralph. "He has stood by me through thick and thin. He did what he thought was best. I see now, from what M. Poirot has told me, that it was not really the best. I should have come forward and faced the music. You see, in the home, we never saw a newspaper. I knew nothing of what was going on."

"You see now why I drew attention to the reticence of your manuscript," murmured Poirot. "It was strictly truthful as far as it went -- but it did not go very far, eh, my friend?"

I was too abashed to argue.

"Dr Sheppard has been a model of discretion," said Poirot drily. "But me, I discover all the little secrets. It is my business."

"Now we can have your story of what happened that night," said Raymond impatiently.

"You know it already," said Ralph. "There's very little for me to all. I left the summer-house about nine forty-five, and tramped about the lanes, trying to make up my mind as to what to do next -- what line to take. I'm bound to admit that I've not the shadow of an alibi, but I give you my solemn word that I never went to the study, that I never saw my stepfather alive -- or dead. Whatever the world thinks, I'd like all of you to believe me."

"You see what I mean? No? Just this -- to save Captain Paton the real criminal must confess." He beamed round at us all.

There was a tense silence. Into the midst of it came the old Breton woman with a telegram on a salver. Poirot tore it open.

"It makes things very simple, though," said Poirot, in a cheerful voice. "Very simple indeed."

Blunt's voice rose abrupt and resonant. "The murderer is amongst us, you say? You know which?"

"No alibi," murmured Raymond. "That's bad. I believe you, of course, but -- it's a bad business."

"But yes -- I mean what I say. See now, I did not invite Inspector Raglan to be present. That was for a reason. I did not want to tell him all that I knew -- at least I did not want to tell him tonight." He leaned forward, and suddenly his voice and his whole personality changed. He suddenly became dangerous.

We all stared at him.

"I who speak to you -- I know the murderer of Mr Ackroyd is in this room now. It is to the murderer I speak. Tomorrow the truth goes to Inspector Raglan. You understand?"

"A wireless message -- from a steamer now on her way to the United States."

"What is that?" said Raymond sharply.

Poirot had read the message. He crumpled it up in his hand.

"Messieurs et Mesdames, this reunion of mine is at an end. Remember -- the truth goes to Inspector Raglan in the morning."

"I know -- now." He tapped the crumpled ball of paper.

There was a dead silence. Poirot rose to his feet bowing.