Ryland had gone to London for the day, taking Appleby with him. Miss Martin and I were strolling together in the garden after tea. I liked the girl very much, she was so unaffected and so natural. I could see that there was 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 hur riedly.

"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 shorttempered.

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 innocentsounding 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. He was starting to keep the appointment. I redoubled my pace, so as to get a clear start. I arrived at the quarry somewhat out of breath. There seemed no one about, and I crawled into a thick tangle of bushes and awaited developments.

Ten minutes later, just on the stroke of eleven, Ryland stalked up, his hat over his eyes and the inevitable cigar in his mouth. He gave a quick look round, and then plunged into the hollows of the quarry below.

Presently I heard a low murmur of voices come up to me. Evidently the other man-or men-whoever they were, had arrived first at the rendezvous. I crawled cautiously out of the bushes, and inch by inch, using the utmost precaution against noise, I wormed myself down the steep path. Only a boulder now separated me from the talking men. Secure in the blackness, I peeped round the edge of it and found myself facing the muzzle of a black, murderous-looking automatic!

"Hands up!" said Mr. Ryland succinctly. "I've been waiting for you."

He was seated in the shadow of the rock, so that I could not see his face, but the menace in his voice was unpleasant. Then I felt a ring of cold steel on the back of my neck, and Ryland lowered his own automatic.

"That's right, George," he drawled. "March him around here."

Raging inwardly, I was conducted to a spot in the shadows, where the unseen George (whom I suspected of being the impeccable Deaves), gagged and bound me securely.

Ryland spoke again in a tone which I had difficulty in recognising, so cold and menacing was it.