"It's very simple. Reuben had been pitching into young Charles - not without good reason, I must say. Later on he tried to bully me. I told him a few home truths and, just to annoy him, I made up my mind to back the boy. I meant to see him that night, so as to tell him how the land lay. When I went up to my room I didn't go to bed. Instead, I left the door ajar and sat on a chair smoking. My room is on the second floor, M. Poirot, and Charles's room is next to it."

"Pardon my interrupting you - Mr Trefusis, he, too, sleeps on that floor?"

Astwell nodded.

"Yes, his room is just beyond mine."

"Nearer the stairs?"

"No, the other way."

A curious light came into Poirot's face, but the other didn't notice it and went on: "As I say, I waited up for Charles. I heard the front door slam, as I thought, about five minutes to twelve, but there was no sign of Charles for about ten minutes. When he did come up the stairs I saw that it was no good tackling him that night.

He lifted his elbows significantly.

"I see," murmured Poirot.

"Poor devil couldn't walk straight," said Astwell. "He was looking pretty ghastly, too. I put it down to his condition at the time. Of course, now I realize that he had come straight from committing the crime."

Poirot interposed a quick question.

"You heard nothing from the Tower room?"

"No but you must remember that I was right at the other end of the building. The walls are thick, and I don't believe you would even hear a pistol shot fired from there."

Poirot nodded.

"I asked if he would like some help getting to bed," continued Astwell. "But he said he was all right and went into his room and banged the door. I undressed and went to bed."

Poirot was staring thoughtfully at the carpet.

"You realize, M. Astwell," he said at last, "that your evidence is very important?"

"I suppose so, at least - what do you mean?"

"Your evidence that ten minutes elapsed between the slamming of the front door and Leverson's appearance upstairs. He himself says, so I understand, that he came into the house and went straight up to bed. But there is more than that. Lady Astwell's accusation of the secretary is fantastic, I admit, yet up to now it has not been proved impossible. But your evidence creates an alibi."

"How is that?"

"Lady Astwell says that she left her husband at a quarter to twelve, while the secretary had gone to bed at eleven o'clock. The only time he could have committed the crime was between a quarter to twelve and Charles Leverson's return. Now, if, as you say, you sat with your door open, he could not have come down from his room without your seeing him."

"That is so," agreed the other.

"There is no other staircase?"

"No, to get down to the Tower room he would have had to pa.s.s my door, and he didn't, I am quite sure of that. And, anyway, M. Poirot, as I said just now, the man is as meek as a parson, I a.s.sure you."

"But yes, but yes," said Poirot soothingly, "I understand all that." He paused. "And you will not tell me the subject of your quarrel with Sir Reuben?"

The other's face turned a dark red.

"You'll get nothing out of me."

Poirot looked at the ceiling.

"I can always be discreet," he murmured, "where a lady is concerned."

Victor Astwell sprang to his feet.

"d.a.m.n you, how did you - what do you mean?"

"I was thinking," said Poirot, "of Miss Lily Margrave."

Victor Astwell stood undecided for a minute or two then his color subsided, and he sat down again.

"You are too clever for me, M. Poirot. Yes, it was Lily we quarreled about. Reuben had his knife into her; he had ferreted out something or other about the girl - false references, something of that kind. I don't believe a word of it myself.

"And then he went further than he had any right to go, talked about her stealing down at night and getting out of the house to meet some fellow or other. My G.o.d! I gave it to him; I told him that better men than he had been killed for saying less. That shut him up. Reuben was inclined to be a bit afraid of me when I got going."

"I hardly wonder at it," murmured Poirot politely.

"I think a lot of Lily Margrave," said Victor in another tone. "A nice girl through and through."

Poirot did not answer. He was staring in front of him, seemingly lost in abstraction. He came out of his brown study with a jerk.

"I must, I think, promenade myself a little. There is a hotel here, yes?"

"Two," said Victor Astwell, "the Golf Hotel up by the links and the Mitre down by the station."

"I thank you," said Poirot. "Yes, certainly I must promenade myself a little."

The Golf Hotel as befits its name, stands on the golf links almost adjoining the club house. It was to this hostelry that Poirot repaired first in the course of that "promenade" which he had advertised himself as being about to take. The little man had his own way of doing things. Three minutes after he had entered the Golf Hotel he was in private consultation with Miss Langdon, the manageress.

"I regret to incommode you in any way, Mademoiselle," said Poirot, "but you see I am a detective."

Simplicity always appealed to him. In this case the method proved efficacious at once.

"A detective!" exclaimed Miss Langdon, looking at him doubtfully.

"Not from Scotland Yard," Poirot a.s.sured her. "In fact - you may have noticed it? I am not an Englishman. No, I make the private inquiries into the death of Sir Reuben Astwell."

"You don't say, now!" Miss Langdon goggled at him expectantly.

"Precisely," said Poirot, beaming. "Only to someone of discretion like yourself would I reveal the fact. I think, Mademoiselle, you may be able to aid me. Can you tell me of any gentleman staying here on the night of the murder who was absent from the hotel that evening and returned to it about twelve or half-past?"

Miss Langdon's eyes opened wider than ever.

"You don't think -?" she breathed.

"That yon had the murderer here? No, but I have reason to believe that a guest staying here promenaded himself in the direction of Mon Repos that night, and if so he may have seen something which, though conveying no meaning to him, might be very useful to me."

The manageress nodded her head sapiently, with an air of one thoroughly well up in the annals of detective law.

"I understand perfectly. Now, let me see; who did we have staying here?"

She frowned, evidently running over the names in her mind, and helping her memory by occasionally checking them off on her fingertips.

"Captain Swann, Mr Elkins, Major Blunt, old Mr Benson. No, really, sir, I don't believe anyone went out that evening."

"You would have noticed if they had done so, eh?"

"Oh, yes, sir, it is not very usual, you see. I mean gentlemen go out to dinner and all that, but they don't go out after dinner, because - well, there is nowhere to go to, is there?"

The attractions of Abbots Cross were golf and nothing but golf.

"That is so," agreed Poirot. "Then, as far as you remember, Mademoiselle, n.o.body from here was out that night?"

"Captain England and his wife were out to dinner."

Poirot shook his head.

"That is not the kind of thing I mean. I will try the other hotel; the Mitre, is it not?"

"Oh, the Mitre," said Miss Langdon. "Of course, anyone might have gone out walking from there."

The disparagement of her tone, though vague, was evident, and Poirot beat a tactful retreat.

Ten minutes later he was repeating the scene this time with Miss Cole, the brusque manageress of the Mitre, a less pretentious hotel with lower prices, situated close to the station.

"There was one gentleman out late that night, came in about half-past twelve, as far as I can remember. Quite a habit of his it was, to go out for a walk at that time of the evening. He had done it once or twice before. Let me see now, what was his name? Just for the moment I can't remember it."

She pulled a large ledger toward her and began turning over the pages.

"Nineteenth, twentieth, twenty-first, twenty-second. Ah, here we are. Naylor, Captain Humphrey Naylor."

"He had stayed here before? You know him well?"

"Once before," said Miss Cole, "about a fortnight earlier. He went out then in the evening, I remember."

"He came to play golf, eh?"

"I suppose so," said Miss Cole; "that's what most of the gentlemen come for."

"Very true," said Poirot. "Well, Mademoiselle, I thank you infinitely, and I wish you good day."

He went back to Mon Repos with a very thoughtful face. Once or twice he drew something from his pocket and looked at it.

"It must be done," he murmured to himself, "and soon, as soon as I can make the opportunity."

His first proceeding on re-entering the house was to ask Parsons where Miss Margrave might be found. He was told that she was in the small study dealing with Lady Astwell's correspondence and the information seemed to afford Poirot satisfaction.

He found the little study without difficulty. Lily Margrave was seated at a desk by the window, writing. But for her the room was empty. Poirot carefully shut the door behind him and came toward the girl.

"I may have a little minute of your time, Mademoiselle, you will be so kind?"

"Certainly."

Lily Margrave put the papers aside and turned toward him.

"What can I do for you?"

"On the evening of the tragedy, Mademoiselle, I understand that when Lady Astwell went to her husband you went straight up to bed. Is that so?"

Lily Margrave nodded.

"You did not come down again, by any chance?"

The girl shook her head.

"I think you said, Mademoiselle, that you had not at any time that evening been in the Tower room?"

"I don't remember saying so, but as a matter of fact that is quite true. I was not in the Tower room that evening."

Poirot raised his eyebrows.

"Curious," he murmured.

"What do you mean?"

"Very curious," murmured Hercule Poirot again. "How do you account, then, for this?"

He drew from his pocket a little sc.r.a.p of stained green chiffon and held it up for the girl's inspection.

Her expression did not change, but he felt rather than heard the sharp intake of breath.

"I don't understand, M. Poirot."

"You wore, I understand, a green chiffon dress that evening, Mademoiselle. This -" he tapped the sc.r.a.p in his fingers - "was torn from it."

"And you found it in the Tower room?" asked the girl sharply. "Whereabouts?"

Hercule Poirot looked at the ceiling.

"For the moment shall we just say - in the Tower room?"

For the first time, a look of fear sprang into the girl's eyes. She began to speak, then checked herself. Poirot watched her small white hands clenching themselves on the edge of the desk.

"I wonder if I did go into the Tower room that evening?" she mused. "Before dinner, I mean. I don't think so. I am almost sure I didn t. If that sc.r.a.p has been in the Tower room all this time, it seems to me a very extraordinary thing the police did not find it right away."