From our quiet retreat in the Ardennes we watched the progress of affairs in the great world. We were plentifully supplied with newspapers, and every day Poirot received a bulky envelope, evidently containing some kind of report. He never showed these reports to me, but I could usually tell from his manner whether its contents had been satisfactory or otherwise. He never wavered in his belief that our present plan was the only one likely to be crowned by success.

"As a minor point, Hastings," he remarked one day, "I was in continual fear of your death lying at my door. And that rendered me nervous—like a cat upon the jumps, as you say. But now I am well satisfied. Even if they discover that the Captain Hastings who landed in South America is an imposter (and I do not think they will discover it, they are not likely to send an agent out there who knows you personally), they will only believe that you are trying to circumvent them in some clever manner of your own, and will pay no serious attention to discovering your whereabouts. Of the one vital fact, my supposed death, they are thoroughly convinced. They will go ahead and mature their plans."

"And then?" I asked eagerly.

"And then, mon ami, grand resurrection of Hercule Poirot! At the eleventh hour I reappear, throw all into confusion, and achieve the supreme victory in my own unique manner!"

I realised that Poirot's vanity was of the case-hardened variety which could withstand all attacks. I reminded him that once or twice the honours of the game had lain with our adversaries. But I might have known that it was impossible to diminish Hercule Poirot's enthusiasm for his own methods.

"See you, Hastings, it is like the little trick that you play with the cards. You have seen it without doubt? You take the four knaves, you divide them, one on top of the pack, one underneath, and so on—you cut and you shuffle, and there they are all together again. That is my object. So far I have been contending, now against one of the Big Four, now against another. But let me get them all together, like the four knaves in the pack of cards, and then, with one coup, I destroy them all!"

"And how do you propose to get them all together?" I asked.

"By awaiting the supreme moment. By lying perdu until they are ready to strike."

"That may mean a long wait," I grumbled.

"Always impatient, the good Hastings! But no, it will not be so long. The one man they were afraid of—myself—is out of the way. I give them two or three months at most."

His speaking of some one being got out of the way reminded me of Ingles and his tragic death, and I remembered that I had never told Poirot about the dying Chinaman in St. Giles' Hospital.

He listened with keen attention to my story.

"Ingles's servant, eh? And the few words he uttered were in Italian? Curious."

"That's why I suspected it might have been a plant on the part of the Big Four."

"Your reasoning is at fault, Hastings. Employ the little gray cells. If your enemies wished to deceive you they would assuredly have seen to it that the Chinaman spoke in intelligible pigeon English. No, the message was genuine. Tell me again all that you heard?"

"First of all he made a reference to Handel's Largo, and then he said something that sounded like 'carrozzo'—that's a carriage, isn't it?"

"Nothing else?"

"Well, just at the end he murmured something like 'Cara' somebody or other—some woman's name. Zia, I think. But I don't suppose that that had any bearing on the rest of it."

"You would not suppose so, Hastings. Cara Zia is very important, very important indeed."

"I don't see—"

"My dear friend, you never see—and anyway the English know no geography."

"Geography?" I cried. "What has geography got to do with it?"

"I dare say M. Thomas Cook would be more to the point."

As usual, Poirot refused to say anything more—a most irritating trick of his. But I noticed that his manner became extremely cheerful, as though he had scored some point or other.

The days went on, pleasant if a trifle monotonous. There were plenty of books in the villa, and delightful rambles all around, but I chafed sometimes at the forced inactivity of our life, and marvelled at Poirot's state of placid content. Nothing occurred to ruffle our quiet existence, and it was not until the end of June, well within the limit that Poirot had given them, that we had our news of the Big Four.

A car drove up to the villa early one morning, such an unusual event in our peaceful life that I hurried down to satisfy my curiosity. I found Poirot talking to a pleasant-faced young fellow of about my own age.

He introduced me.

"This is Captain Harvey, Hastings, one of the most famous members of your Intelligence Service."

"Not famous at all, I'm afraid," said the young man, laughing pleasantly.

"Not famous except to those in the know, I should have said. Most of Captain Harvey's friends and acquaintances consider him an amiable but brainless young man—devoted only to the trot of the fox or whatever the dance is called."

We both laughed.

"Well, well, to business," said Poirot. "You are of opinion the time has come, then?"

"We are sure of it, sir. China was isolated politically yesterday. What is going on out there, nobody knows. No news of any kind, wireless or otherwise, has come through—just a complete break—and silence!"

"Li Chang Yen has shown his hand. And the others?"

"Abe Ryland arrived in England a week ago, and left for the Continent yesterday."

"And Madame Olivier?"

"Madame Olivier left Paris last night."

"For Italy?"

"For Italy, sir. As far as we can judge, they are both making for the resort you indicated—though how you knew that—"

"Ah, that is not the cap with the feather for me! That was the work of Hastings here. He conceals his intelligence, you comprehend, but it is profound for all that."

Harvey looked at me with due appreciation, and I felt rather uncomfortable.

"All is in train, then," said Poirot. He was pale now, and completely serious. "The time has come. The arrangements are all made?"

"Everything you ordered has been carried out. The governments of Italy, France and England are behind you, and are all working harmoniously together."

"It is, in fact, a new Entente," observed Poirot dryly. "I am glad that Desjardeaux is convinced at last. Eh bien, then, we will start—or rather, I will start. You, Hastings, will remain here—yes, I pray of you. In verity, my friend, I am serious."

I believed him, but it was not likely that I should consent to being left behind in that fashion. Our argument was short but decisive.

It was not until we were in the train, speeding towards Paris that he admitted that he was secretly glad of my decision.

"For you have a part to play, Hastings. An important part! Without you, I might well fail. Nevertheless, I felt that it was my duty to urge you to remain behind."

"There is danger, then?"

"Mon ami, where there is the Big Four there is always danger."

On arrival in Paris, we drove across to the Gare de l'Est, and Poirot at last announced our destination. We were bound for Bolzano and Italian Tyrol.

During Harvey's absence from our carriage I took the opportunity of asking Poirot why he had said that the discovery of the rendezvous was my work.

"Because it was, my friend. How Ingles managed to get hold of the information I do not know, but he did, and he sent it to us by his servant. We are bound, mon ami for Karersee, the new Italian name for which is Lago di Carezza. You see now where your 'Cara Zia' comes in and also your 'Carrozza' and 'Largo'—the Handel was supplied by your own imagination. Possibly some reference to the information coming from the 'hand' of M. Ingles started the train of association."

"Karersee?" I queried. "I never heard of it."

"I always tell you that the English know no geography. But as a matter of fact it is a well-known and very beautiful summer resort, four thousand feet up, in the heart of the Dolomites."

"And it is in this out of the way spot that the Big Four have their rendezvous?"

"Say rather their headquarters. The signal has been given and it is their intention to disappear from the world and issue orders from their mountain fastness. I have made the inquiries—a lot of quarrying of stone and mineral deposits is done there, and the company, apparently a small Italian firm, is in reality controlled by Abe Ryland. I am prepared to swear that a vast subterranean dwelling has been hollowed out in the very heart of the mountain, secret and inaccessible. From there the leaders of the organisation will issue by wireless their orders to their followers who are numbered by thousands in every country. And from that crag in the Dolomites the dictators of the world will emerge. That is to say—they would emerge were it not for Hercule Poirot."

"Do you seriously believe all this, Poirot? What about the armies and general machinery of civilisation?"

"What about it in Russia, Hastings? This will be Russia on an infinitely larger scale—and with this additional menace—that Madame Olivier's experiments have proceeded further than she has ever given out. I believe that she has, to a certain extent, succeeded in liberating atomic energy and harnessing it to her purpose. Her experiments with the nitrogen of the air have been very remarkable, and she has also experimented in the concentration of wireless energy, so that a beam of great intensity can be focused upon some given spot. Exactly how far she has progressed, nobody knows, but it is certain that it is much farther than has ever been given out. She is a genius, that woman—the Curies were as nothing to her. Add to her genius the powers of Ryland's almost unlimited wealth, and, with the brain of Li Chang Yen, the finest criminal brain ever known, to direct and plan—eh bien, it will not be, as you say, all jam for civilisation."

His words made me very thoughtful. Although Poirot was given at times to exaggeration of language, he was not really an alarmist. For the first time I realised what a desperate struggle it was upon which we were engaged.

Harvey soon rejoined us and the journey went on.

We arrived at Bolzano about midday. From there the journey on was by motor. Several big blue motor-cars were waiting in the central square of the town, and we three got into one of them. Poirot, notwithstanding the heat of the day, was muffled to the eyes in greatcoat and scarf. His eyes and the tips of his ears were all that could be seen of him.

I did not know whether this was due to precaution or merely his exaggerated fear of catching a chill. The motor journey took a couple of hours. It was a really wonderful drive. For the first part of the way we wound in and out of huge cliffs, with a trickling waterfall on one hand. Then we emerged into a fertile valley, which continued for some miles, and then, still winding steadily upwards, the bare rocky peaks began to show with dense clustering pine woods at their base. The whole place was wild and lovely. Finally a series of abrupt curves, with the road running through the pine woods on either side, and we came suddenly upon a big hotel and found that we had arrived.

Our rooms had been reserved for us, and under Harvey's guidance we went straight up to them. They looked straight out over the rocky peaks and the long slopes of pine woods leading up to them. Poirot made a gesture towards them.

"It is there?" he asked in a low voice.

"Yes," replied Harvey. "There is a place called the Felsenlabyrynth—all big boulders piled about in a most fantastic way—a path winds through them. The quarrying is to the right of that, but we think that the entrance is probably in the Felsenlabyrynth."

Poirot nodded.

"Come, mon ami," he said to me. "Let us go down and sit upon the terrace and enjoy the sunlight."

"You think that wise?" I asked.

He shrugged his shoulders.

The sunlight was marvellous—in fact the glare was almost too great for me. We had some creamy coffee instead of tea, then went upstairs and unpacked our few belongings. Poirot was in his most unapproachable mood, lost in a kind of reverie. Once or twice he shook his head and sighed.

I had been rather intrigued by a man who had got out of our train at Bolzano, and had been met by a private car. He was a small man, and the thing about him that had attracted my attention was that he was almost as much muffled up as Poirot had been. More so, indeed, for in addition to greatcoat and muffler, he was wearing huge blue spectacles. I was convinced that here we had an emissary of the Big Four. Poirot did not seem very impressed by my idea, but when, leaning out of my bedroom window, I reported that the man in question was strolling about in the vicinity of the hotel, he admitted that there might be something in it.

I urged my friend not to go down to dinner, but he insisted on doing so. We entered the dining-room rather late, and were shown to a table by the window. As we sat down, our attention was attracted by an exclamation and a crash of falling china. A dish of haricots verts had been upset over a man who was sitting at the table next to ours.

The head waiter came up and was vociferous in apologies.

Presently, when the offending waiter was serving us with soup, Poirot spoke to him.

"An unfortunate accident, that. But it was not your fault."

"Monsieur saw that? No, indeed it was not my fault. The gentleman half sprung up from his chair—I thought he was going to have an attack of some kind. I could not save the catastrophe."

I saw Poirot's eyes shining with the green light I knew so well, and as the waiter departed he said to me in a low voice:—

"You see, Hastings, the effect of Hercule Poirot—alive and in the flesh?"

"You think—"

I had not time to continue. I felt Poirot's hand on my knee, as he whispered excitedly:

"Look, Hastings, look. His trick with the bread! Number Four!"

Sure enough, the man at the next table to ours, his face unusually pale, was dabbing a small piece of bread mechanically about the table.

I studied him carefully. His face, clean-shaven and puffily fat, was of a pasty, unhealthy sallowness, with heavy pouches under the eyes and deep lines running from his nose to the corners of his mouth. His age might have been anything from thirty-five to forty-five. In no particular did he resemble any one of the characters which Number Four had previously assumed. Indeed, had it not been for his little trick with the bread, of which he was evidently quite unaware, I would have sworn readily enough that the man sitting there was some one whom I had never seen before.

"He has recognised you," I murmured. "You should not have come down."

"My excellent Hastings, I have feigned death for three months for this one purpose."

"To startle Number Four?"

"To startle him at a moment when he must act quickly or not at all. And we have this great advantage—he does not know that we recognise him. He thinks that he is safe in his new disguise. How I bless Flossie Monro for telling us of that little habit of his."

"What will happen now?" I asked.

"What can happen? He recognises the only man he fears, miraculously resurrected from the dead, at the very minute when the plans of the Big Four are in the balance. Madame Olivier and Abe Ryland lunched here to-day, and it is thought that they went to Cortina. Only we know that they have retired to their hiding place. How much do we know? That is what Number Four is asking himself at this minute. He dare take no risks. I must be suppressed at all costs. Eh bien, let him try to suppress Hercule Poirot! I shall be ready for him."

As he finished speaking, the man at the next table got up and went out.

"He has gone to make his little arrangements," said Poirot placidly. "Shall we have our coffee on the terrace, my friend? It would be pleasanter, I think. I will just go up and get a coat."

I went out on to the terrace, a little disturbed in mind. Poirot's assurance did not quite content me. However, so long as we were on our guard, nothing could happen to us. I resolved to keep thoroughly on the alert.

It was quite five minutes before Poirot joined me. With his usual precautions against cold, he was muffled up to the ears. He sat down beside me and sipped his coffee appreciatively.

"Only in England is the coffee so atrocious," he remarked. "On the continent they understand how important it is for the digestion that it should be properly made."

As he finished speaking, the man from the next table suddenly appeared on the terrace. Without any hesitation, he came over and drew up a third chair to our table.

"You do not mind my joining you, I hope," he said in English.

"Not at all, monsieur," said Poirot.

I felt very uneasy. It is true that we were on the terrace of the hotel, with people all round us, but nevertheless I was not satisfied. I sensed the presence of danger.

Meanwhile Number Four chatted away in a perfectly natural manner. It seemed impossible to believe that he was anything but a bona fide tourist. He described excursions and motor trips, and posed as quite an authority on the neighbourhood.

He took a pipe from his pocket and began to light it. Poirot drew out his case of tiny cigarettes. As he placed one between his lips, the stranger leant forward with a match.

"Let me give you a light."

As he spoke, without the least warning, all the lights went out. There was a chink of glass, and something pungent under my nose, suffocating me—