reen light. I bent forward, peering into the place beyond,
but was unable to perceive anything save a vague greenness.

And as I peered, half believing that the whole episode was a
dreadful, fevered dream, the abominable fumes of hashish grew, or
seemed to grow, quite suddenly insupportable. Through the square
opening, from the green void beyond, a cloud of oily vapour, pungent,
stifling, resembling that of burning Indian hemp, poured out and
enveloped me!

With a gasping cry I fell back, fighting for breath, for a breath
of clean air unpolluted with hashish. But every inhalation drew
down into my lungs the fumes that I sought to escape from. I
experienced a deathly sickness; I seemed to be sinking into a sea
of hashish, amid bubbles of yellow and green and gold, and I knew
no more until, struggling again to my feet, surrounded by utter
darkness--I struck my head on the corner of my writing-table ... for
I lay in my own study!

My revolver, unloaded, was upon the table beside me. The night was
very still. I think it must have been near to dawn.

"My God!" I whispered, "did I dream it all? Did I dream it all?"

CHAPTER XXI

THE BLACK TUBE

"There's no doubt in my mind," said Inspector Bristol, "that your
experience was real enough."

The sun was shining into my room now, but could not wholly disperse
the cloud of horror which lay upon it. That I had been drugged was
sufficiently evident from my present condition, and that I had been
taken away from my chambers Inspector Bristol had satisfactorily
proved by an examination of the soles of my slippers.

"It was a clever trick," he said. "God knows what it was they
puffed into your face through the letter box, but the devilish arts
of ten centuries, we must remember, are at the command of Hassan of
Aleppo! The repetition of the trick at the mysterious place you
were taken to is particularly interesting. I should say you won't
be in a hurry to peer through letter boxes and so forth in the
future?"

I shook my aching head.

"That accursed yellow room," I replied, "stank with the fumes of
hashish. It may have been some preparation of hashish that was
used to drug me."

Bristol stood looking thoughtfully from the window.

"It was a nightmare business, Mr. Cavanagh," he said; "but it
doesn't advance our inquiry a little bit. The prophecy of the old
man with the white beard--whom you assure me to be none other than
Hassan of Aleppo--is somet