I inhaled deeply and glanced across at my companion.  Beneath the make-up with which I had stained my skin, I knew that I had grown more than a little pale.

“Fletcher!” I whispered, “we are on the eve of a great discovery—­that girl ...”

I broke off, and clutching the table with both hands, sat listening intently.  From the room behind me, the opium-room, whose entrance was less than two paces from where we sat, came a sound of dragging and tapping!  Slowly, cautiously, I began to turn my head; when a sudden outburst of simian chattering from the fan-tan players drowned that other sinister sound.

“You heard it, Doctor!” hissed Fletcher.

“The man with the limp!” I said hoarsely; “he is in there!  Fletcher!  I am utterly confused.  I believe this place to hold the key to the whole mystery, I believe ...”

Fletcher gave me a warning glance—­and, turning anew, I saw Zarmi approaching with her sinuous gait, carrying two glasses and jug upon the ornate tray.  These she set down upon the table; then stood spinning the salver cleverly upon the point of her index finger and watching us through half-closed eyes.

My companion took out some loose coins, but the girl thrust the proffered payment aside with her disengaged hand, the salver still whirling upon the upraised finger of the other.

“Presently you pay for drink,” she said.  “You do something for me—­eh?”

“Yep,” replied Fletcher nonchalantly, watering the rum in the tumblers.  “What time?”

“Presently I tell you.  You stay here.  This one a strong feller?”—­ indicating myself.

“Sure,” drawled Fletcher; “strong as a mule he is.”

“All right.  I give him one little kiss if he good boy!”

Tossing the tray in the air she caught it, rested its edge upon her hip, turned, and walked away down the room, puffing her cigarette.

“Listen,” I said, bending across the table, “it was Zarmi who drove the cab that came for Nayland Smith to-day!”

“My God!” whispered Fletcher, “then it was nothing less than the hand of Providence that brought us here to-night.  Yes!  I know how you feel, Doctor!—­but we must play our cards as they’re dealt to us.  We must wait—­wait.”

Out from the den of the opium-smokers came Zarmi, one hand resting upon her hip and the other uplifted, a smoldering yellow cigarette held between the first and second fingers.  With a movement of her eyes she summoned us to join her, then turned and disappeared again through the low doorway.

The time for action was arrived—­we were to see behind the scenes of the Joy-Shop!  Our chance to revenge poor Smith even if we could not save him.  I became conscious of an inward and suppressed excitement; surreptitiously I felt the hilt of the Browning pistol in my pocket.  The shadow of the dead Fu-Manchu seemed to be upon me.  God! how I loathed and feared that memory!