The creaking of the oars sounded muffled and ghostly, and none of the men in the boat seemed to be inclined to converse.  Heading across stream they made for the unseen promontory of the Isle of Dogs.  Navigation was suspended, and they reached midstream without seeing a ship’s light.  Then came the damp wind again to lift the fog, and ahead of them they discerned one of the General Steam Navigation Company’s boats awaiting an opportunity to make her dock at the head of Deptford Creek.  The clamor of an ironworks on the Millwall shore burst loudly upon their ears, and away astern the lights of the Surrey Dock shone out once more.  Hugging the bank they pursued a southerly course, and from Limehouse Reach crept down to Greenwich Reach.

Fog closed in upon them, a curtain obscuring both light and sound.  When the breeze came again it had gathered force, and it drove the mist before it in wreathing banks, and brought to their ears a dull lowing and to their nostrils a farmyard odor from the cattle pens.  Ghostly flames, leaping and falling, leaping and falling, showed where a gasworks lay on the Greenwich bank ahead.

Eastward swept the river now, and fresher blew the breeze.  As they rounded the blunt point of the “Isle” the fog banks went swirling past them astern, and the lights on either shore showed clearly ahead.  A ship’s siren began to roar somewhere behind them.  The steamer which they had passed was about to pursue her course.

Closer in-shore drew the boat, passing a series of wharves, and beyond these a tract of waste, desolate bank very gloomy in the half light and apparently boasting no habitation of man.  The activities of the Greenwich bank seemed remote, and the desolation of the Isle of Dogs very near, touching them intimately with its peculiar gloom.

A light sprang into view some little distance inland, notable because it shone lonely in an expanse of utter blackness.  Kerry broke the long silence.

“Dougal’s,” he said.  “Put us ashore here.”

The police boat was pulled in under a rickety wooden structure, beneath which the Thames water whispered eerily; and Kerry and Seton disembarked, mounting a short flight of slimy wooden steps and crossing a roughly planked place on to a shingly slope.  Climbing this, they were on damp waste ground, pathless and uninviting.

“Dougal’s is being watched,” said Kerry.  “I think I told you?”

“Yes,” replied Seton.  “But I have formed the opinion that the dope gang is too clever for the ordinary type of man.  Sin Sin Wa is an instance of what I mean.  Neither you nor I doubt that he is a receiver of drugs—­perhaps the receiver; but where is our case?  The only real link connecting him with the West-End habitue is his wife.  And she has conveniently deserted him!  We cannot possibly prove that she hasn’t while he chooses to maintain that she has.”

“H’m,” grunted Kerry, abruptly changing the subject.  “I hope I’m not recognized here.”