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."