Seated there in that Limehouse attic, a smoky lamp burning on the table between them, and one gripping the stump of a cheroot between his teeth, while the other chewed steadily, they presented a combination which none but a fool would have lightly challenged.

“Sin Sin Wa is cunning,” said Seton suddenly.  “He is a very clever man.  Watch him as closely as you like, he will never lead you to the ‘store.’  In the character of John Smiles I had some conversation with him this morning, and I formed the same opinion as yourself.  He is waiting for something; and he is certain of his ground.  I have a premonition, Chief Inspector, that whoever else may fall into the net, Sin Sin Wa will slip out.  We have one big chance.”

“What’s that?” rapped Kerry.

“The dope syndicate can only have got control of ‘the traffic’ in one way—­by paying big prices and buying out competitors.  If they cease to carry on for even a week they lose their control.  The people who bring the stuff over from Japan, South America, India, Holland, and so forth will sell somewhere else if they can’t sell to Kazmah and Company.  Therefore we want to watch the ships from likely ports, or, better still, get among the men who do the smuggling.  There must be resorts along the riverside used by people of that class.  We might pick up information there.”

Kerry smiled savagely.

“I’ve got half a dozen good men doing every dive from Wapping to Gravesend,” he answered.  “But if you think it worth looking into personally, say the word.”

“Well, my dear sir,”—­Seton Pasha tossed the end of his cheroot into the empty grate—­“what else can we do?”

Kerry banged his fist on the table.

“You’re right!” he snapped.  “We’re stuck!  But anything’s better than nothing.  We’ll start here and now; and the first joint we’ll make for is Dougal’s.”

“Dougal’s?” echoed Seton Pasha.

“That’s it—­Dougal’s.  A danger spot on the Isle of Dogs used by the lowest type of sea-faring men and not barred to Arabs, Chinks, and other gaily-colored fowl.  If there’s any chat going on about dope, we’ll hear it in Dougal’s.”

Seton Pasha stood up, smiling grimly.  “Dougal’s it shall be,” he said.

CHAPTER XXXII

ON THE ISLE OF DOGS

As the police beat left Limehouse Pier, a clammy south-easterly breeze blowing up-stream lifted the fog in clearly defined layers, an effect very singular to behold.  At one moment a great arc-lamp burning above the Lavender Pond of the Surrey Commercial Dock shot out a yellowish light across the Thames.  Then, as suddenly as it had come, the light vanished again as a stratum of mist floated before it.