"What was there in the letter, I wonder, to upset him so?"
"Absolutely nothing - that's just the curious part of it.
I had read it before I discovered my mistake.
It was quite short.
I can still remember it word for word, and there was nothing in it that could possibly upset any one."
"You can repeat it, you say?" I encouraged her.
"Yes." She paused a minute and then repeated slowly, whilst I noted down the words unobtrusively, the following:
"Dear Sir, "The essential thing now, I should say, is to see the property.
If you insist on the quarry being included, then seventeen thousand seems reasonable.
11% commission too much, 4% is ample. "Yours truly, "Arthur Leversham."
Miss Martin went on:
"Evidently about some property Mr. Ryland was thinking of buying.
But really, I do feel that a man who can get into a rage over such a trifle is, well, dangerous.
What do you think I ought to do, Major Neville?
You've more experience of the world than I have."
I soothed the girl down, pointed out to her that Mr. Ryland had probably been suffering from the enemy of his race - dyspepsia.
In the end I sent her away quite comforted.
But I was not so easily satisfied myself.
When the girl had gone, and I was alone, I took out my notebook, and ran over the letter which I had jotted down.
What did it mean - this apparently innocent-sounding missive?
Did it concern some business deal which Ryland was undertaking, and was he anxious that no details about it should leak out until it was carried through?
That was a possible explanation.
But I remembered the small figure 4 with which the envelopes were marked, and I felt that, at last, I was on the track of the thing we were seeking.
I puzzled over the letter all that evening, and most of the next day - and then suddenly the solution came to me.
It was so simple, too.
The figure 4 was the clue.
Read every fourth word in the letter, and an entirely different message appeared.
"Essential should see you quarry seventeen eleven four." The solution of the figures was easy.
Seventeen stood for the seventeenth of October - which was tomorrow, eleven was the time, and four was the signature - either referring to the mysterious Number Four himself - or else it was the "trade-mark" so to speak, of the Big Four.
The quarry was also intelligible.
There was a big disused quarry on the estate about half a mile from the house - a lonely spot, ideal for a secret meeting.
For a moment or two I was tempted to run the show myself.
It would be such a feather in my cap, for once, to have the pleasure of crowing over Poirot.
But in the end I overcame the temptation.
This was a big business - I had no right to play a lone hand, and perhaps jeopardise our chances of success.
For the first time, we had stolen a march upon our enemies.
We must make good this time - and, disguise the fact as I might, Poirot had the better brain of the two.
I wrote off post haste to him, laying the facts before him, and explaining how urgent it was that we should overhear what went on at the interview.
If he liked to leave it to me, well and good, but I gave him detailed instructions how to reach the quarry from the station in case he should deem it wise to be present himself.
I took the letter down to the village and posted it myself.
I had been able to communicate with Poirot throughout my stay, by the simple expedient of posting my letters myself, but we had agreed that he should not attempt to communicate with me in case my letters should be tampered with.
I was in a glow of excitement the following evening.
No guests were staying in the house, and I was busy with Mr. Ryland in his study all the evening.
I had foreseen that this would be the case, which was why I had had no hope of being able to meet Poirot at the station.
I was, however, confident that I would be dismissed well before eleven o'clock.
Sure enough, just after ten-thirty, Mr. Ryland glanced at the clock, and announced that he was "through."
I took the hint and retired discreetly.
I went upstairs as though going to bed, but slipped quietly down a side staircase and let myself out into the garden, having taken the precaution to don a dark overcoat to hide my white shirtfront.
I had gone some way down the garden when I chanced to look over my shoulder.
Mr. Ryland was just stepping out from his study window into the garden.