hashish den is in some adjoining building?"

"I don't know where it is, Petrie, but I know the way to it!"

Into a narrow, gloomy court we plunged, hemmed in by high walls, and
followed it for ten yards or more. An even narrower and less inviting
turning revealed itself on the left. We pursued our way, and presently
found ourselves at the back of the Cafe de l'Egypte.

"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,