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, Kâramaneh, 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 Kâramaneh'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 remains. I have no positive evidence, but I would wager all I possess that there is a stair in the thickness of the wall, and hidden doors in the paneling of the three apartments. The Yellow group has somehow obtained possession of a plan of the historic secret passages and chambers of Graywater Park. Homopoulo is the spy in the household; and Sir Lionel, with his man Kennedy, was removed directly the invitation to us had been posted. The group will know by now that we have escaped them, but Kâramaneh …"
 
"Smith!" I groaned, "Smith! What can we do? What has befallen her? …"
 
"This way!" he snapped. "We are not beaten yet!"
 
"We must arouse the servants!"
 
"Why? It would be sheer waste of priceless time. There are only three men who actually sleep in the house (excepting Homopoulo) and these are in the northwest wing. No, Petrie; we must rely upon ourselves."
 
He was racing recklessly along the tortuous corridors and up the oddly placed stairways of that old-world building. My anguish had reinforced the atropine which I had employed as an antidote to the opiate in the wine, and now my blood, that had coursed sluggishly, leapt through my veins like fire and I burned with a passionate anger.
 
Into a large and untidy bedroom we burst. Books and papers littered about the floor; curios, ranging from mummied cats and ibises to Turkish yataghans and Zulu assegais, surrounded the place in riotous disorder. Beyond doubt this was the apartment of Sir Lionel Barton. A lamp burned upon a table near to the disordered bed, and a discolored Greek statuette of Orpheus lay overturned on the carpet close beside it.
 
"Homopoulo was on the point of leaving this room at the moment that I peered in at the window," said Smith, breathing heavily. "From here there is another entrance to the secret passages. Have your pistol ready."
 
He stepped across the disordered room to a little alcove near the foot of the bed, directing the ray of the pocket-lamp upon the small, square paneling.
 
"Ah!" he cried, a note of triumph in his voice—"he has left the door ajar! A visit of inspection was not anticipated to-night, Petrie! Thank God for an Indian liver and a suspicious mind."
 
He disappeared into a yawning cavity which now I perceived to exist in the wall. I hurried after him, and found myself upon roughly fashioned stone steps in a very low and narrow descending passage. Over his shoulder—
 
"Note the direction," said Smith breathlessly. "We shall presently find ourselves at the base of the east tower."
 
Down we went and down, the ray of the electric lamp always showing more steps ahead, until at last these terminated in a level, arched passage, curving sharply to the right. Two paces more brought us to a doorway, less, than four feet high, approached by two wide steps. A blackened door, having a most cumbersome and complicated lock, showed in the recess.
 
Nayland Smith bent and examined the mechanism intently.
 
"Freshly oiled!" he commented. "You know into whose room it opens?"
 
Well enough I knew, and, detecting that faint, haunting perfume which spoke of the dainty personality of Kâramaneh, my anger blazed up anew. Came a faint sound of metal grating upon metal, and Smith pulled open the door, which turned outward upon the steps, and bent further forward, sweeping the ray of light about the room beyond.
 
"Empty, of course!" he muttered. "Now for the base of these damned nocturnal operations."
 
He descended the steps and began to flash the light all about the arched passageway wherein we stood.
 
"The present dining-room of Graywater Park lies almost due south of this spot," he mused. "Suppose we try back."
 
We retraced our steps to the foot of the stair. In the wall on their left was an opening, low down against the floor and little more than three feet high; it reminded me of some of the entrances to those seemingly interminable passages whereby one approaches the sepulchral chambers of the Egyptian Pyramids.
 
"Now for it!" snapped Smith. "Follow me closely."
 
Down he dropped, and, having the lamp thrust out before him, began to crawl into the tunnel. As his heels disappeared, and only a faint light outlined the opening, I dropped upon all fours in turn, and began laboriously to drag myself along behind him. The atmosphere was damp, chilly, and evil-smelling; therefore, at the end of some ten or twelve yards of this serpentine crawling, when I saw Smith, ahead of me, to be standing erect, I uttered a stifled exclamation of relief. The thought of Kâramaneh having been dragged through this noisome hole was one I dared not dwell upon.
 
A long, narrow passage now opened up, its end invisible from where we stood. Smith hurried forward. For the first thirty of forty paces the roof was formed of massive stone slabs; then its character changed; the passage became lower, and one was compelled frequently to lower the head in order to avoid the oaken beams which crossed it.
 
"We are passing under the dining-room," said Smith. "It was from here the sound of beating first came!"
 
"What do you mean?"
 
"I have built up a theory, which remains to be proved, Petrie. In my opinion a captive of the Yellow group escaped to-night and sought to summon assistance, but was discovered and overpowered."
 
"Sir Lionel?"
 
"Sir Lionel, or Kennedy—yes, I believe so."
 
Enlightenment came to m............