!" I cried.

"Impossible!" snapped Smith.

"What do you mean?"

"Sir Lionel has disappeared!"

CHAPTER XXXVI

THE DUNGEON

We were out in the corridor now, Smith showing the way with the light
of his electric pocket-lamp. My mind was clear enough, but I felt as
weak as a child.

"You look positively ghastly, old man," rapped Smith, "which is no
matter for wonder. I have yet to learn how it happened that you are
not lying insensible, or dead, as a result of the drugged wine. When
I heard some one moving in your room, it never occurred to me that it
was _you_."

"Smith," I said--"the house seems as still as death."

"You, Karamaneh, and myself are the only occupants of the east wing.
Homopoulo saw to that."

"Then he----"

"He is a member of the Si-Fan, a creature of Dr. Fu-Manchu--yes,
beyond all doubt! Sir Lionel is unfortunate--as ever--in his choice
of servants. I blame my own stupidity entirely, Petrie; and I pray
that my enlightenment has not come too late."

"What does it all mean?--what have you learnt?"

"Mind these three steps," warned Smith, glancing back. "I found my
mind persistently dwelling upon the matter of that weird rapping,
Petrie, and I recollected the situation of Sir Lionel's room, on the
southeast front. A brief inspection revealed the fact that, by means
of a kindly branch of ivy, I could reach the roof of the east tower
from my window."

"Well?"

"One may walk from there along the roof of the southeast front, and
by lying face downwards at the point where it projects above the main
entrance look into Sir Lionel's room!"

"I saw you go!"

"I feared that some one was watching me, but that it was you I had
never supposed. Neither Barton nor his man are in that room, Petrie!
They have been spirited away! This is Karamaneh's door."

He grasped me by the arm, at the same time directing the light upon a
closed door before which we stood. I raised my fist and beat upon the
panels; then, every muscle tensed and my heart throbbing wildly, I
listened for the girl's voice.

Not a sound broke that deathly stillness except the beating of my own
heart, which, I thought, must surely be audible to my companion.
Frantically I hurled myself against the stubborn oak, but Smith thrust
me back.

"Useless, Petrie!" he said--"useless. This room is in the base of the
east tower, yours is above it and mine at the top. The corridors
approaching the three floors deceive one, but the fact