“Take me first to the River Police Station,” I directed; “along Ratcliffe Highway.”

The man turned and nodded comprehendingly, as I could see through the wet pane.

Presently we swerved to the right and into an even narrower street.  This inclined in an easterly direction, and proved to communicate with a wide thoroughfare along which passed brilliantly lighted electric trams.  I had lost all sense of direction, and when, swinging to the left and to the right again, I looked through the window and perceived that we were before the door of the Police Station, I was dully surprised.

In quite mechanical fashion I entered the depot.  Inspector Ryman, our associate in one of the darkest episodes of the campaign with the Yellow Doctor two years before, received me in his office.

By a negative shake of the head, he answered my unspoken question.

“The ten o’clock boat is lying off the Stone Stairs, Doctor,” he said, “and co-operating with some of the Scotland Yard men who are dragging that district—­”

I shuddered at the word “dragging”; Ryman had not used it literally, but nevertheless it had conjured up a dread possibility—­a possibility in accordance with the methods of Dr. Fu-Manchu.  All within space of an instant I saw the tide of Limehouse Reach, the Thames lapping about the green-coated timbers of a dock pier; and rising—­falling—­ sometimes disclosing to the pallid light a rigid hand, sometimes a horribly bloated face—­I saw the body of Nayland Smith at the mercy of those oily waters.  Ryman continued: 

“There is a launch out, too, patrolling the riverside from here to Tilbury.  Another lies at the breakwater”—­he jerked his thumb over his shoulder.  “Should you care to take a run down and see for yourself?”

“No, thanks,” I replied, shaking my head.  “You are doing all that can be done.  Can you give me the address of the place to which Mr. Smith went last night?”

“Certainly,” said Ryman; “I thought you knew it.  You remember Shen-Yan’s place—­by Limehouse Basin?  Well, further east—­east of the Causeway, between Gill Street and Three Colt Street—­is a block of wooden buildings.  You recall them?”

“Yes,” I replied.  “Is the man established there again, then?”

“It appears so, but, although you have evidently not been informed of the fact, Weymouth raided the establishment in the early hours of this morning!”

“Well?” I cried.

“Unfortunately with no result,” continued the inspector.  “The notorious Shen-Yan was missing, and although there is no real doubt that the place is used as a gaming-house, not a particle of evidence to that effect could be obtained.  Also—­there was no sign of Mr. Nayland Smith, and no sign of the American, Burke, who had led him to the place.”

“Is it certain that they went there?”

“Two C. I. D. men who were shadowing, actually saw the pair of them enter.  A signal had been arranged, but it was never given; and at about half past four, the place was raided.”