“Was there a gallery outside the window?”

“No; it was impossible to climb to right or left of the window or up on to the roof.  I convinced myself of that.”

“But, my dear man!” I cried, “you are eliminating every natural mode of egress!  Nothing remains but flight.”

“I am aware, Petrie, that nothing remains but flight; in other words I have never to this day understood how she quitted the room.  I only know that she did.”

“And then?”

“I saw in this incredible escape the cunning hand of Dr. Fu-Manchu—­ saw it at once.  Peace was ended; and I set to work along certain channels without delay.  In this manner I got on the track at last, and learned, beyond the possibility of doubt, that the Chinese doctor lived—­nay! was actually on his way to Europe again!”

There followed a short silence.  Then: 

“I suppose it’s a mystery that will be cleared up some day,” concluded Smith; “but to date the riddle remains intact.”  He glanced at the clock.  “I have an appointment with Weymouth; therefore, leaving you to the task of solving this problem which thus far has defied my own efforts, I will get along.”

He read a query in my glance.

“Oh!  I shall not be late,” he added; “I think I may venture out alone on this occasion without personal danger.”

Nayland Smith went upstairs to dress, leaving me seated at my writing table, deep in thought.  My notes upon the renewed activity of Dr. Fu-Manchu were stacked at my left hand, and, opening a new writing block, I commenced to add to them particulars of this surprising event in Rangoon which properly marked the opening of the Chinaman’s second campaign.  Smith looked in at the door on his way out, but seeing me thus engaged, did not disturb me.

I think I have made it sufficiently evident in these records that my practice was not an extensive one, and my hour for receiving patients arrived and passed with only two professional interruptions.

My task concluded, I glanced at the clock, and determined to devote the remainder of the evening to a little private investigation of my own.  From Nayland Smith I had preserved the matter a secret, largely because I feared his ridicule; but I had by no means forgotten that I had seen, or had strongly imagined that I had seen, Karamaneh—­that beautiful anomaly, who (in modern London) asserted herself to be a slave—­in the shop of an antique dealer not a hundred yards from the British Museum!

A theory was forming in my brain, which I was burningly anxious to put to the test.  I remembered how, two years before, I had met Karamaneh near to this same spot; and I had heard Inspector Weymouth assert positively that Fu-Manchu’s headquarters were no longer in the East End, as of yore.  There seemed to me to be a distinct probability that a suitable center had been established for his reception in this place, so much less likely to be suspected by the authorities.