I have met people who enjoy a channel crossing; men who can sit calmly in their deck-chairs and, on arrival, wait until the boat is moored, then gather their belongings together without fuss and disembark. Personally, I can never manage this. From the moment I get on board I feel that the time is too short to settle down to anything. I move my suit-cases from one spot to another, and if I go down to the saloon for a meal, I bolt my food with an uneasy feeling that the boat may arrive unexpectedly whilst I am below. Perhaps all this is merely a legacy from one's short leaves in the war, when it seemed a matter of such importance to secure a place near the gangway, and to be amongst the first to disembark lest one should waste precious minutes of one's three or five days' leave.

On this particular July morning, as I stood by the rail and watched the white cliffs of Dover drawing nearer, I marvelled at the passengers who could sit calmly in their chairs and never even raise their eyes for the first sight of their native land. Yet perhaps their case was different from mine. Doubtless many of them had only crossed to Paris for the week-end, whereas I had spent the last year and a half on a ranch in the Argentine. I had prospered there, and my wife and I had both enjoyed the free and easy life of the South American continent, nevertheless it was with a lump in my throat that I watched the familiar shore draw nearer and nearer.

I had landed in France two days before, transacted some necessary business, and was now en route for London. I should be there some months—time enough to look up old friends, and one old friend in particular. A little man with an egg-shaped head and green eyes—Hercule Poirot! I proposed to take him completely by surprise. My last letter from the Argentine had given no hint of my intended voyage—indeed, that had been decided upon hurriedly as a result of certain business complications—and I spent many amused moments picturing to myself his delight and stupefaction on beholding me.

He, I knew, was not likely to be far from his headquarters. The time when his cases had drawn him from one end of England to the other was past. His fame had spread, and no longer would he allow one case to absorb all his time. He aimed more and more, as time went on, at being considered a "consulting detective"—as much a specialist as a Harley Street physician. He had always scoffed at the popular idea of the human bloodhound who assumed wonderful disguises to track criminals, and who paused at every footprint to measure it.

"No, my friend Hastings," he would say; "we leave that to Giraud and his friends. Hercule Poirot's methods are his own. Order and method, and 'the little gray cells.' Sitting at ease in our own arm-chairs we see the things that these others overlook, and we do not jump to the conclusion like the worthy Japp."

No; there was little fear of finding Hercule Poirot far afield.

On arrival in London, I deposited my luggage at an hotel and drove straight on to the old address. What poignant memories it brought back to me! I hardly waited to greet my old landlady, but hurried up the stairs two at a time and rapped on Poirot's door.

"Enter, then," cried a familiar voice from within.

I strode in. Poirot stood facing me. In his arms he carried a small valise, which he dropped with a crash on beholding me.

"Mon ami, Hastings!" he cried. "Mon ami, Hastings!"

And, rushing forward, he enveloped me in a capacious embrace. Our conversation was incoherent and inconsequent. Ejaculations, eager questions, incomplete answers, messages from my wife, explanations as to my journey, were all jumbled up together.

"I suppose there's some one in my old rooms?" I asked at last, when we had calmed down somewhat. "I'd love to put up here again with you."

Poirot's face changed with startling suddenness.

"Mon Dieu! but what a chance épouvantable. Regard around you, my friend."

For the first time I took note of my surroundings. Against the wall stood a vast ark of a trunk of prehistoric design. Near to it were placed a number of suit-cases, ranged neatly in order of size from large to small. The inference was unmistakable.

"You are going away?"

"Yes."

"Where to?"

"South America."

"What?"

"Yes, it is a droll farce, is it not? It is to Rio I go, and every day I say to myself, I will write nothing in my letters—but oh! the surprise of the good Hastings when he beholds me!"

"But when are you going?"

Poirot looked at his watch.

"In an hour's time."

"I thought you always said nothing would induce you to make a long sea voyage?"

Poirot closed his eyes and shuddered.

"Speak not of it to me, my friend. My doctor, he assures me that one dies not of it—and it is for the one time only; you understand, that never—never shall I return."

He pushed me into a chair.

"Come, I will tell you how it all came about. Do you know who is the richest man in the world? Richer even than Rockefeller? Abe Ryland."

"The American Soap King?"

"Precisely. One of his secretaries approached me. There is some very considerable, as you would call it, hocus-pocus going on in connection with a big company in Rio. He wished me to investigate matters on the spot. I refused. I told him that if the facts were laid before me, I would give him my expert opinion. But that he professed himself unable to do. I was to be put in possession of the facts only on my arrival out there. Normally, that would have closed the matter. To dictate to Hercule Poirot is sheer impertinence. But the sum offered was so stupendous that for the first time in my life I was tempted by mere money. It was a competence—a fortune! And there was a second attraction—you, my friend. For this last year and a half I have been a very lonely old man. I thought to myself, Why not? I am beginning to weary of this unending solving of foolish problems. I have achieved sufficient fame. Let me take this money and settle down somewhere near my old friend."

I was quite affected by this token of Poirot's regard.

"So I accepted," he continued, "and in an hour's time I must leave to catch the boat train. One of life's little ironies, is it not? But I will admit to you, Hastings, that had not the money offered been so big, I might have hesitated, for just lately I have begun a little investigation of my own. Tell me, what is commonly meant by the phrase, 'The Big Four'?"

"I suppose it had its origin at the Versailles Conference, and then there's the famous 'Big Four' in the film world, and the term is used by hosts of smaller fry."

"I see," said Poirot thoughtfully. "I have come across the phrase, you understand, under certain circumstances where none of those explanations would apply. It seems to refer to a gang of international criminals or something of that kind; only—"

"Only what?" I asked, as he hesitated.

"Only that I fancy that it is something on a large scale. Just a little idea of mine, nothing more. Ah, but I must complete my packing. The time advances."

"Don't go," I urged. "Cancel your passage and come out on the same boat with me."

Poirot drew himself up and glanced at me reproachfully.

"Ah, it is that you do not understand! I have passed my word, you comprehend—the word of Hercule Poirot. Nothing but a matter of life or death could detain me now."

"And that's not likely to occur," I murmured ruefully. "Unless at the eleventh hour 'the door opens and the unexpected guest comes in.'"

I quoted the old saw with a slight laugh, and then, in the pause that succeeded it, we both started as a sound came from the inner room.

"What's that?" I cried.

"Ma foi!" retorted Poirot. "It sounds very like your 'unexpected guest' in my bedroom."

"But how can any one be in there? There's no door except into this room."

"Your memory is excellent, Hastings. Now for the deductions."

"The window! But it's a burglar then? He must have had a stiff climb of it—I should say it was almost impossible."

I had risen to my feet and was striding in the direction of the door when the sound of a fumbling at the handle from the other side arrested me.

The door swung slowly open. Framed in the doorway stood a man. He was coated from head to foot with dust and mud; his face was thin and emaciated. He stared at us for a moment, and then swayed and fell. Poirot hurried to his side, then he looked up and spoke to me.

"Brandy—quickly."

I dashed some brandy into a glass and brought it. Poirot managed to administer a little, and together we raised him and carried him to the couch. In a few minutes he opened his eyes and looked round him with an almost vacant stare.

"What is it you want, monsieur?" said Poirot.

The man opened his lips and spoke in a queer mechanical voice.

"M. Hercule Poirot, 14 Farraway Street."

"Yes, yes; I am he."

The man did not seem to understand, and merely repeated in exactly the same tone:—

"M. Hercule Poirot, 14 Farraway Street."

Poirot tried him with several questions. Sometimes the man did not answer at all; sometimes he repeated the same phrase. Poirot made a sign to me to ring up on the telephone.

"Get Dr. Ridgeway to come round."

The doctor was in luckily; and as his house was only just round the corner, few minutes elapsed before he came bustling in.

"What's all this, eh?"

Poirot gave a brief explanation, and the doctor started examining our strange visitor, who seemed quite unconscious of his presence or ours.

"H'm!" said Dr. Ridgeway, when he had finished. "Curious case."

"Brain fever?" I suggested.

The doctor immediately snorted with contempt.

"Brain fever! Brain fever! No such thing as brain fever. An invention of novelists. No; the man's had a shock of some kind. He's come here under the force of a persistent idea—to find M. Hercule Poirot, 14 Farraway Street—and he repeats those words mechanically without in the least knowing what they mean."

"Aphasia?" I said eagerly.

This suggestion did not cause the doctor to snort quite as violently as my last one had done. He made no answer, but handed the man a sheet of paper and a pencil.

"Let's see what he'll do with that," he remarked.

The man did nothing with it for some moments, then he suddenly began to write feverishly. With equal suddenness he stopped and let both paper and pencil fall to the ground. The doctor picked it up, and shook his head.

"Nothing here. Only the figure 4 scrawled a dozen times, each one bigger than the last. Wants to write 14 Farraway Street, I expect. It's an interesting case—very interesting. Can you possibly keep him here until this afternoon? I'm due at the hospital now, but I'll come back this afternoon and make all arrangements about him. It's too interesting a case to be lost sight of."

I explained Poirot's departure and the fact that I proposed to accompany him to Southampton.

"That's all right. Leave the man here. He won't get into mischief. He's suffering from complete exhaustion. Will probably sleep for eight hours on end. I'll have a word with that excellent Mrs. Funnyface of yours, and tell her to keep an eye on him."

And Dr. Ridgeway bustled out with his usual celerity. Poirot hastily completed his packing, with one eye on the clock.

"The time, it marches with a rapidity unbelievable. Come now, Hastings, you cannot say that I have left you with nothing to do. A most sensational problem. The man from the unknown. Who is he? What is he? Ah, sapristi, but I would give two years of my life to have this boat go to-morrow instead of to-day. There is something here very curious—very interesting. But one must have time—time. It may be days—or even months—before he will be able to tell us what he came to tell."

"I'll do my best, Poirot," I assured him. "I'll try to be an efficient substitute."

"Ye-es."

His rejoinder struck me as being a shade doubtful. I picked up the sheet of paper.

"If I were writing a story," I said lightly, "I should weave this in with your latest idiosyncrasy and call it The Mystery of the Big Four." I tapped the pencilled figures as I spoke.

And then I started, for our invalid, roused suddenly from his stupor, sat up in his chair and said clearly and distinctly:

"Li Chang Yen."

He had the look of a man suddenly awakened from sleep. Poirot made a sign to me not to speak. The man went on. He spoke in a clear, high voice, and something in his enunciation made me feel that he was quoting from some written report or lecture.

"Li Chang Yen may be regarded as representing the brains of the Big Four. He is the controlling and motive force. I have designated him, therefore, as Number One. Number Two is seldom mentioned by name. He is represented by an 'S' with two lines through it—the sign for a dollar; also by two stripes and a star. It may be conjectured, therefore, that he is an American subject, and that he represents the power of wealth. There seems no doubt that Number Three is a woman, and her nationality French. It is possible that she may be one of the sirens of the demi-monde but nothing is known definitely. Number Four—"

His voice faltered and broke. Poirot leant forward.

"Yes," he prompted eagerly. "Number Four?"

His eyes were fastened on the man's face. Some overmastering terror seemed to be gaining the day; the features were distorted and twisted.

"The destroyer," gasped the man. Then, with a final convulsive movement, he fell back in a dead faint.

"Mon Dieu!" whispered Poirot, "I was right then. I was right."

"You think—?"

He interrupted me.

"Carry him on to the bed in my room. I have not a minute to lose if I would catch my train. Not that I want to catch it. Oh, that I could miss it with a clear conscience! But I gave my word. Come, Hastings!"

Leaving our mysterious visitor in the charge of Mrs. Pearson, we drove away, and duly caught the train by the skin of our teeth. Poirot was alternately silent and loquacious. He would sit staring out of the window like a man lost in a dream, apparently not hearing a word that I said to him. Then, reverting to animation suddenly, he would shower injunctions and commands upon me, and urge the necessity of constant marconigrams.

We had a long fit of silence just after we passed Woking. The train, of course, did not stop anywhere until Southampton; but just here it happened to be held up by a signal.

"Ah! Sacré mille tonnerres!" cried Poirot suddenly. "But I have been an imbecile. I see clearly at last. It is undoubtedly the blessed saints who stopped the train. Jump, Hastings, but jump, I tell you."

In an instant he had unfastened the carriage door, and jumped out on the line.

"Throw out the suit-cases and jump yourself."

I obeyed him. Just in time. As I alighted beside him, the train moved on.

"And now Poirot," I said, in some exasperation, "perhaps you will tell me what all this is about."

"It is, my friend, that I have seen the light."

"That," I said, "is very illuminating to me."

"It should be," said Poirot, "but I fear—I very much fear that it is not. If you can carry two of these valises, I think I can manage the rest."