Dusk always brought with it a cloud of apprehensions, for darkness must ever be the ally of crime; and it was one night, long after the clocks had struck the mystic hour “when churchyards yawn,” that the hand of Dr. Fu-Manchu again stretched out to grasp a victim.  I was dismissing a chance patient.

“Good night, Dr. Petrie,” he said.

“Good night, Mr. Forsyth,” I replied; and, having conducted my late visitor to the door, I closed and bolted it, switched off the light and went upstairs.

My patient was chief officer of one of the P. and O. boats.  He had cut his hand rather badly on the homeward run, and signs of poisoning having developed, had called to have the wound treated, apologizing for troubling me at so late an hour, but explaining that he had only just come from the docks.  The hall clock announced the hour of one as I ascended the stairs.  I found myself wondering what there was in Mr. Forsyth’s appearance which excited some vague and elusive memory.  Coming to the top floor, I opened the door of a front bedroom and was surprised to find the interior in darkness.

“Smith!” I called.

“Come here and watch!” was the terse response.  Nayland Smith was sitting in the dark at the open window and peering out across the common.  Even as I saw him, a dim silhouette, I could detect that tensity in his attitude which told of high-strung nerves.

I joined him.

“What is it?” I said, curiously.

“I don’t know.  Watch that clump of elms.”

His masterful voice had the dry tone in it betokening excitement.  I leaned on the ledge beside him and looked out.  The blaze of stars almost compensated for the absence of the moon and the night had a quality of stillness that made for awe.  This was a tropical summer, and the common, with its dancing lights dotted irregularly about it, had an unfamiliar look to-night.  The clump of nine elms showed as a dense and irregular mass, lacking detail.

Such moods as that which now claimed my friend are magnetic.  I had no thought of the night’s beauty, for it only served to remind me that somewhere amid London’s millions was lurking an uncanny being, whose life was a mystery, whose very existence was a scientific miracle.

“Where’s your patient?” rapped Smith.

His abrupt query diverted my thoughts into a new channel.  No footstep disturbed the silence of the highroad; where was my patient?

I craned from the window.  Smith grabbed my arm.

“Don’t lean out,” he said.

I drew back, glancing at him surprisedly.

“For Heaven’s sake, why not?”

“I’ll tell you presently, Petrie.  Did you see him?”

“I did, and I can’t make out what he is doing.  He seems to have remained standing at the gate for some reason.”

“He has seen it!” snapped Smith.  “Watch those elms.”

His hand remained upon my arm, gripping it nervously.  Shall I say that I was surprised?  I can say it with truth.  But I shall add that I was thrilled, eerily; for this subdued excitement and alert watching of Smith could only mean one thing: