Fu-Manchu touched some hidden bell.  A hideous yellow man with a scarred face entered, carrying a tray upon which were a bowl containing some steaming fluid, apparently soup, what looked like oaten cakes, and a flask of red wine.

As the boy, exhibiting no more unusual symptoms than if he had just awakened from a normal sleep, commenced his repast, Karamaneh drew me gently along the passage into the room which we had first entered.  My heart leaped wildly as the marmoset bounded past us to drop hand over hand to the lower apartment in search of its master.

“You see,” said Karamaneh, her voice quivering, “he is not dead!  But without Fu-Manchu he is dead to me.  How can I leave him when he holds the life of Aziz in his hand?”

“You must get me that flask, or some of its contents,” I directed.  “But tell me, how does he produce the appearance of death?”

“I cannot tell you,” she replied.  “I do not know.  It is something in the wine.  In another hour Aziz will be again as you saw him.  But see.”  And, opening a little ebony box, she produced a phial half filled with the amber liquid.

“Good!” I said, and slipped it into my pocket.  “When will be the best time to seize Fu-Manchu and to restore your brother?”

“I will let you know,” she whispered, and, opening the door, pushed me hurriedly from the room.  “He is going away to-night to the north; but you must not come to-night.  Quick!  Quick!  Along the passage.  He may call me at any moment.”

So, with the phial in my pocket containing a potent preparation unknown to Western science, and with a last long look into the eyes of Karamaneh, I passed out into the narrow alley, out from the fragrant perfumes of that mystery house into the place of Thames-side stenches.

CHAPTER XXII

“We must arrange for the house to be raided without delay,” said Smith.  “This time we are sure of our ally—­”

“But we must keep our promise to her,” I interrupted.

“You can look after that, Petrie,” my friend said. 
“I will devote the whole of my attention to Dr. Fu-Manchu!”
he added grimly.

Up and down the room he paced, gripping the blackened briar between his teeth, so that the muscles stood out squarely upon his lean jaws.  The bronze which spoke of the Burmese sun enhanced the brightness of his gray eyes.

“What have I all along maintained?” he jerked, looking back at me across his shoulder—­“that, although Karamaneh was one of the strongest weapons in the Doctor’s armory, she was one which some day would be turned against him.  That day has dawned.”

“We must await word from her.”

“Quite so.”

He knocked out his pipe on the grate.  Then: 

“Have you any idea of the nature of the fluid in the phial?”

“Not the slightest.  And I have none to spare for analytical purposes.”