“There’s the door,” I said.

It opened into a tiny cul de sac, flanked by dilapidated hoardings, and no other door of any kind was visible in the vicinity.  Nayland Smith stood tugging at the lobe of his ear almost savagely.

“Where the devil do they go?” he whispered.

Even as he spoke the words, came a gleam of light through the upper curtained part of the door, and I distinctly saw the figure of a man in silhouette.

“Stand back!” snapped Smith.

We crouched back against the dirty wall of the court, and watched a strange thing happen.  The back door of the Cafe de l’Egypte opened outward, simultaneously a door, hitherto invisible, set at right angles in the hoarding adjoining, opened inward!

A man emerged from the cafe and entered the secret doorway.  As he did so, the cafe door swung back ... and closed the door in the hoarding!

“Very good!” muttered Nayland Smith.  “Our friend Ismail, behind the counter, moves some lever which causes the opening of one door automatically to open the other.  Failing his kindly offices, the second exit from the Cafe de l’Egypte is innocent enough.  Now—­what is the next move?”

“I have an idea, Smith!” I cried.  “According to Morrison, the place in which the hashish may be obtained has no windows but is lighted from above.  No doubt it was built for a studio and has a glass roof.  Therefore——­”

“Come along!” snapped Smith, grasping my arm; “you have solved the difficulty, Petrie.”

CHAPTER XXV

THE HOUSE OF HASHISH

Along the leads from Frith Street we worked our perilous way.  From the top landing of a French restaurant we had gained access, by means of a trap, to the roof of the building.  Now, the busy streets of Soho were below me, and I clung dizzily to telephone standards and smoke stacks, rarely venturing to glance downward upon the cosmopolitan throng, surging, dwarfish, in the lighted depths.

Sometimes the bulky figure of Inspector Weymouth would loom up grotesquely against the star-sprinkled blue, as he paused to take breath; the next moment Nayland Smith would be leading the way again, and I would find myself contemplating some sheer well of blackness, with nausea threatening me because it had to be negotiated.

None of these gaps were more than a long stride from side to side; but the sense of depth conveyed in the muffled voices and dimmed footsteps from the pavements far below was almost overpowering.  Indeed, I am convinced that for my part I should never have essayed that nightmare journey were it not that the musical voice of Karamaneh seemed to be calling to me, her little white hands to be seeking mine, blindly, in the darkness.

That we were close to a haunt of the dreadful Chinamen I was persuaded; therefore my hatred and my love cooperated to lend me a coolness and address which otherwise I must have lacked.