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 æsthetic, probably 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 mountain-side.

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.

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. the trick has succeeded."

"this is achille poirot," i said slowly. "hercule poirot's twin brother."

"impossible," said ryland sharply, but he was shaken.

"hercule'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?"

ryland was staring at achille poirot.

"suppose he's lying," he said hoarsely.

the other shrugged his shoulders.

"in an hour it will be dawn. then you can see for yourself the truth of my words. already they should have traced me to the entrance in the felsenlabyrynth."

even as he spoke, there was a far off reverberation, and a man ran in shouting incoherently. ryland sprang up and went out. madame olivier moved to the end of the room and opened a door that i had not noticed. inside i caught a glimpse of a perfectly equipped laboratory which reminded me of the one in paris. number four also sprang up and went out. he returned with poirot's revolver which he gave to the countess.

"there is no danger of their escaping," he said grimly. "but still you had better have this."

then he went out again.

the countess came over to us and surveyed my companion attentively for some time. suddenly she laughed.

"you are very clever, m. achille poirot," she said mockingly.

"madame, let us talk business. it is fortunate that they have left us alone together. what is your price?"

"i do not understand. what price?"

"madame, you can aid us to escape. you know the secret ways out of this retreat. i ask you, what is your price?"

she laughed again.

"more than you could pay, little man! why, all the money in the world would not buy me!"

"madame, i did not speak of money. i am a man of intelligence. nevertheless, this is a true fact—everyone has his price. in exchange for life and liberty, i offer you your heart's desire."

"so you are a magician!"

"you can call me so if you like."

the countess suddenly dropped her jesting manner. she spoke with passionate bitterness.

"fool! my heart's desire! can you give me revenge upon my enemies? can you give me back youth and beauty and a gay heart? can you bring the dead to life again?"

achille poirot was watching her very curiously.

"which of the three, madame? make your choice."

she laughed sardonically.

"you will sell me the elixir of life, perhaps? come, i will make a bargain with you. once, i had a child. find my child for me—and you shall go free."

"madame, i agree. it is a bargain. your child shall be restored to you. on the faith of—on the faith of hercule poirot himself."

again that strange woman laughed—this time long and unrestrainedly.

"my dear m. poirot, i am afraid i laid a little trap for you. it is very kind of you to promise to find my child for me, but, you see, i happen to know that you would not succeed, and so that would be a very one-sided bargain, would it not?"

"madame, i swear to you by the holy angels that i will restore your child to you."

"i asked you before, m. poirot, could you restore the dead to life?"

"then the child is—"

"dead? yes."

he stepped forward and took her wrist.

"madame, i—i who speak to you, swear once more. i will bring the dead to life."

she stared at him as though fascinated.

"you do not believe me. i will prove my words. get my pocket-book which they took from me."

she went out of the room, and returned with it in her hand. throughout all she retained her grip on the revolver. i felt that achille poirot's chances of bluffing her were very slight. the countess vera rossakoff was no fool.

"open it, madame. the flap on the left-hand side. that is right. now take out that photograph and look at it."

wonderingly, she took out what seemed to be a small snapshot. no sooner had she looked at it than she uttered a cry and swayed as though about to fall. then she almost flew at my companion.

"where? where? you shall tell me. where?"

"remember your bargain, madame."

"yes, yes, i will trust you. quick, before they come back."

catching him by the hand, she drew him quickly and silently out of the room. i followed. from the outer room she led us into the tunnel by which we had first entered, but a short way along this forked, and she turned off to the right. again and again the passage divided, but she led us on, never faltering or seeming to doubt her way, and with increasing speed.

"if only we are in time," she panted. "we must be out in the open before the explosion occurs."

still we went on. i understood that this tunnel led right through the mountain and that we should finally emerge on the other side, facing a different valley. the sweat streamed down my face, but i raced on.

and then, far away, i saw a gleam of daylight. nearer and nearer. i saw green bushes growing. we forced them aside, pushed our way through. we were in the open again, with the faint light of dawn making everything rosy.

poirot's cordon was a reality. even as we emerged, three men fell upon us, but released us again with a cry of astonishment.

"quick," cried my companion. "quick—there is no time to lose—"

but he was not destined to finish. the earth shook and trembled under our feet, there was a terrific roar and the whole mountain seemed to dissolve. we were flung headlong through the air.

i came to myself at last. i was in a strange bed and a strange room. some one was sitting by the window. he turned and came and stood by me.

it was achille poirot—or, stay, was it—

the well-known ironical voice dispelled any doubts i might have had.

"but yes, my friend, it is i. brother achille has gone home again—to the land of myths. it was i all the time. it is not only number four who can act a part. belladona in the eyes, the sacrifice of the moustaches, and a real scar the inflicting of which caused me much pain two months ago—but i could not risk a fake beneath the eagle eyes of number four. and the final touch, your own knowledge and belief that there was such a person as achille poirot! it was invaluable, the assistance you rendered me, half the success of the coup is due to you! the whole crux of the affair was to make them believe that hercule poirot was still at large directing operations. otherwise, everything was true, the aniseed, the cordon, etc."

"but why not really send a substitute?"

"and let you go into danger without me by your side? you have a pretty idea of me there! besides, i always had a hope of finding a way out through the countess."

"how on earth did you manage to convince her? it was a pretty thin story to make her swallow—all that about a dead child."

"the countess has a great deal more perspicacity than you have, my dear hastings. she was taken in at first by my disguise; but she soon saw through it. when she said, 'you are very clever, m. achille poirot,' i knew that she had guessed the truth. it was then or never to play my trump card."

"all that rigmarole about bringing the dead to life?"

"exactly—but then, you see, i had the child all along."

"what?"

"but yes! you know my motto—be prepared. as soon as i found that the countess rossakoff was mixed up with the big four, i had every possible inquiry made as to her antecedents. i learnt that she had had a child who was reported to have been killed, and i also found that there were discrepancies in the story which led me to wonder whether it might not, after all, be alive. in the end, i succeeded in tracing the boy, and by paying out a big sum i obtained possession of the child's person. the poor little fellow was nearly dead of starvation. i placed him in a safe place, with kindly people, and took a snapshot of him in his new surroundings. and so, when the time came, i had my little coup de théâtre all ready!"

"you are wonderful, poirot; absolutely wonderful!"

"i was glad to do it, too. for i had admired the countess. i should have been sorry if she had perished in the explosion."

"i've been half afraid to ask you—what of the big four?"

"all the bodies have now been recovered. that of number four was quite unrecognisable, the head blown to pieces. i wish—i rather wish it had not been so. i should have liked to be sure—but no more of that. look at this."

he handed me a newspaper in which a paragraph was marked. it reported the death, by suicide, of li chang yen, who had engineered the recent revolution which had failed so disastrously.

"my great opponent," said poirot gravely. "it was fated that he and i should never meet in the flesh. when he received the news of the disaster here, he took the simplest way out. a great brain, my friend, a great brain. but i wish i had seen the face of the man who was number four.... supposing that, after all—but i romance. he is dead. yes, mon ami, together we have faced and routed the big four; and now you will return to your charming wife, and i—i shall retire. the great case of my life is over. anything else will seem tame after this. no, i shall retire. possibly i shall grow vegetable marrows! i might even marry and range myself!"

he laughed heartily at the idea, but with a touch of embarrassment. i hope ... small men always admire big, flamboyant women—

"marry and range myself," he said again. "who knows?"