The Big Four by Agatha Christie

something on her mind, and at last out it came.
    “Do you know. Major Neville,” she said, “I am really thinking of resigning my post here.”
    I looked somewhat astonished, and she went on hurriedly.
    “Oh! I know it's a wonderful job to have got, in a way. I suppose most people would think me a fool to throw it up. But I can't stand abuse, Major Neville. To be sworn at like a trooper is more than I can bear. No gentleman would do such a thing.”
    “Has Ryland been swearing at you?”
    She nodded.
    “Of course, he's always rather irritable and short-tempered. That one expects. It's all in the day's work. But to fly into such an absolute fury - over nothing at all. He really looked as though he could have murdered me! And, as I say, over nothing at all!”
    “Tell me about it?” I said, keenly interested.
    “As you know, I open all Mr. Ryland's letters. Some I hand on to Mr. Appleby, others I deal with myself, but I do all the preliminary sorting. Now there are certain letters that come, written on blue paper, and with a tiny 4 marked on the corner - I beg your pardon, did you speak?”
    I had been unable to repress a stifled exclamation, but I hurriedly shook my head, and begged her to continue.
    “Well, as I was saying, these letters come, and there are strict orders that they are never to be opened, but to be handed over to Mr. Ryland intact. And, of course, I always do so. But there was an unusually heavy mail yesterday morning, and I was opening the letters in a terrific hurry. By mistake I opened one of these letters. As soon as I saw what I had done, I took it to Mr. Ryland and explained. To my utter amazement he flew into the most awful rage. As I tell you, I was quite frightened.”
    “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