I could not have been unconscious more than a minute.

I came to myself being hustled along between two men.

They had me under each arm, supporting my weight, and there was a gag in my mouth. It was pitch dark, but I gathered that we were not outside, but passing through the hotel. All round I could hear people shouting and demanding in every known language what had happened to the lights. My captors swung me down some stairs. We passed along a basement passage, then through a door and out into the open again through a glass door at the back of the hotel. In another moment we had gained the shelter of the pine trees.

I had caught a glimpse of another figure in a similar plight to myself, and realised that Poirot, too, was a victim of this bold coup.

By sheer audacity. Number Four had won the day. He had employed, I gathered, an instant anaesthetic, prob205 ably ethyl chloride-breaking a small bulb of it under our noses. Then, in the confusion of the darkness, his accomplices, who had probably been guests sitting at the next table, had thrust gags in our mouths and hurried us away, taking us through The hotel to baffle pursuit.

I cannot describe the hour that followed. We were hurried through the woods at a break-neck pace, going uphill the whole time. At last we emerged in the open, on the mountain-side, and I saw just in front of us an extraordinary conglomeration of fantastic rocks and boulders.

This must be the Felsenlabyrynth of which Harvey had spoken. Soon we were winding in and out of its recesses. The place was like a maze devised by some evil genie.

Suddenly we stopped. An enormous rock barred our path. One of the men stooped and seemed to push on something when, without a sound, the huge mass of rock turned on itself and disclosed a small tunnel-like opening leading into the mountainside.

Into this we were hurried. For some time the tunnel was narrow, but presently it widened, and before very long we came out into a wide rocky chamber lighted by electricity. There the gags were removed. At a sign from Number Four, who stood facing us with mocking triumph in his face, we were searched and every article was removed from our pockets, including Poirot's little automatic pistol.

A pang smote me as it was tossed down on the table.

We were defeated-hopelessly defeated and outnumbered.

It was the end.

"Welcome to the headquarters of the Big Four, M.

Hercule Poirot," said Number Four in a mocking tone.

"To meet you again is an unexpected pleasure. But was it worth while returning from the grave only for this?"

Poirot did not reply. I dared not look at him.

"Come this way," continued Number Four. "Your arrival will be somewhat of a surprise to my colleagues."

He indicated a narrow doorway in the wall. We passed through and found ourselves in another chamber.

At the very end of it was a table behind which four chairs were placed. The end chair was empty, but was draped with a mandarin's cape. On the second, smoking a cigar, sat Mr. Abe Ryland. Leaning back in the third chair, with her burning eyes and her nun's face, was Madame Olivier. Number Four took his seat on the fourth chair.

We were in the presence of the Big Four.

Never before had I felt so fully the reality and the presence of Li Chang Yen as I did now when confronting his empty seat. Far away in China, he yet controlled and directed this malign organisation.

Madame Olivier gave a faint cry on seeing us. Ryland, more self-controlled, only shifted his cigar, and raised his grizzled eyebrows.

"M. Hercule Poirot," said Ryland slowly. "This is a pleasant surprise. You put it over on us all right. We thought you were good and buried. No matter, the game is up now."

There was a ring as of steel in his voice. Madame Olivier said nothing, but her eyes burned, and I disliked the slow way she smiled.

"Madame and messieurs^ I wish you good-evening," said Poirot quietly.

Something unexpected, something I had not been prepared to hear in his voice made me look at him. He seemed quite composed. Yet there was something about his whole appearance that was different.

Tli w Then there was a stir of draperies behind us, and the Countess Vera Rossakoff came in.

"Ah!" said Number Four. "Our valued and trusted lieutenant. An old friend of yours is here, my dear lady."

The countess whirled round with her usual vehemence of movement.

"God in Heaven!" she cried. "It is the little man!

Ah! but he has the nine lives of a cat! Oh, little man, little man! Why did you mix yourself up in this?"

"Madame," said Poirot, with a bow. "Me, like the great Napoleon, I am on the side of the big battalions."

As he spoke I saw a sudden suspicion flash into her eyes, and at the same moment I knew the truth which subconsciously I already sensed.

The man beside me was not Hercule Poirot.

He was very like him, extraordinarily like him. There was the same egg-shaped head, the same strutting figure, delicately plump. But the voice was different, and the eyes instead of being green were dark, and surely the moustaches-those famous moustaches-?

My reflections were cut short by the countess's voice.

She stepped forward, her voice ringing with excitement.

"You have been deceived. That man is not Hercule Poirot!"

Number Four uttered an incredulous exclamation, but the countess leant forward and snatched at Poirot's moustaches. They came off in her hand, and then, indeed, the truth was plain. For this man's upper lip was disfigured by a small scar which completely altered the expression of the face.

"Not Hercule Poirot," muttered Number Four. "But who can he be then?"

"I know," I cried suddenly, and then stopped dead, afraid I had ruined everything.

But the man I will still refer to as Poirot had turned to me encouragingly.

"Say it if you will. It makes no matter now. Thelrick has succeeded."

"This is Achille Poirot," I said slowly. "Hercule Poirot's twin brother."

"Impossible," said Ryland sharply, but he was shaken.

"Hercute's plan has succeeded to a marvel," said Achille placidly.

Number Four leapt forward, his voice harsh and menacing.

"Succeeded, has it?" he snarled. "Do you realise that before many minutes have passed you will be dead- dead?"

"Yes," said Achille Poirot gravely. "I realise that. It is you who do not realise that a man may be willing to purchase success by his life. There were men who laid down their lives for their country in the war. I am prepared to lay down mine in the same way for the world."

It struck me just then that although perfectly willing to lay down my life I might have been consulted in the matter. Then I remembered how Poirot had urged me to stay behind, and I felt appeased.

"And in what way will your laying down your life benefit the world?" asked Ryland sardonically.

"I see that you do not perceive the true inwardness of Hercule's plan. To begin with, your place of retreat was known some months ago, and practically all the visitors, hotel assistants and others are detectives or Secret Service men. A cordon has been drawn round the mountain.

You may have more than one means of egress, but even so you cannot escape. Poirot himself is directing the operations outside. My boots were smeared with a preparation of aniseed to-night, before I came down to the terrace in my brother's place. Hounds are following the trail. It will lead them infallibly to the rock in the Felsenlabyrynth where the entrance is situated. You see, do what you will to us, the net is drawn tightly round you.

You cannot escape."

Madame Olivier laughed suddenly.

"You are wrong. There is one way we can escape, and, like Samson of old, destroy our enemies at the same time. What do you say, my friends?"