"You see," said Bristol, "the Hashishin must know that the safe won't remain here unopened much longer. They will therefore probably make another attempt to-night."  
"It seems likely," I replied; and was silent. Outside the open windows whispered the shrubbery, as a soft breeze stole through the bushes. Beyond, the moon made play in the dim avenue. From the old chapel hard by the sweet-toned bell proclaimed midnight. Our vigil was begun. In this room it was that Professor Deeping had met death at the hands of the murderous Easterns; here it was that Marden and West had mysteriously been struck down the night before.
 
To-night was every whit as hot, and Bristol and I had the windows widely opened. My companion was seated where the detective, Marden, had sat, in a chair near the westerly window, and I lay back in the armchair that had been occupied by West.
 
I may repeat here that the house of the late Professor Deeping was more properly a cottage, surrounded by a fairly large piece of ground, for the most part run wild. The room used as a study was on the ground floor, and had windows on the west and on the south. Those on the west (French windows) opened on a loggia; those on the south opened right into the dense tangle of a neglected shrubbery. The place possessed an oppressive atmosphere of loneliness, for which in some measure its history may have been responsible.
 
The silence, seemingly intensified by each whisper that sped through the elms and crept about the shrubbery, grew to such a stillness that I told myself I had experienced nothing like it since crossing with a caravan I had slept in the desert. Yet noisy, whirling London was within gunshot of us; and this, though hard enough to believe, was a reflection oddly comforting. Only one train of thought was possible, and this I pursued at random.
 
By what means were Marden and West struck down? In thus exposing ourselves, in order that we might trap the author or authors of the outrage, did we act wisely?
 
"Bristol," I said suddenly, "it was someone who came through the open window."
 
"No one," he replied, "came through the windows. West saw absolutely nothing. But if any one comes that way to-night, we have him!"
 
"West may have seen nothing; but how else could any one enter?"
 
Bristol offered no reply; and I plunged again into a maze of speculation.
 
Powerful mantraps were set in such a way that any one or anything, ignorant of their positions, coming up to the windows must unavoidably be snared. These had been placed in position with much secrecy after dusk, and the man on duty at the gate stood with his back to the wall. No one could approach him except from the front. My thoughts took a new turn.
 
Was the girl with the violet eyes an ally of the Hashishin? Thus far, although she so palpably had tricked me, I had found myself unable to speak of her to Bristol; for the idea had entered my mind that she might have learned of the plan to murder Deeping without directly being implicated. Now came yet another explanation. The publicity given to that sensational case might have interested some third party in the fate of the stolen slipper! Could it be that others, in no way connected with the dreadful Hassan of Aleppo, were in quest of the slipper?
 
Scotland Yard had taken care to ensure that the general public be kept in ignorance of the existence of such an organization as the Hashishin, but I must assume that this hypothetical third party were well aware that they had Hassan, as well as the authorities, to count with. Granting the existence of such a party, my beautiful acquaintance might be classified as one of its members. I spoke again.
 
"Bristol," I said, "has it occurred to you that there may be others, as well as Hassan of Aleppo, seeking to gain possession of the sacred slipper?"
 
"It has not," he replied. "In the strictest sense of the expression, they would be out for trouble! What gave you the idea?"
 
"I hardly know," I returned evasively, for even now I was loath to betray the mysterious girl with the wonderful eyes.
 
The chapel bell sounding the half-hour, Bristol rose with a sigh that might have been one of relief, and went out to take the report of the man on duty at the gate. As his footsteps died away along the elm avenue, it came to me how, in the darkness about, menace lurked; and I felt myself succumbing to the greatest dread experienced by man—the dread of the unknown.
 
All that I knew of the weird group of fanatics—survivals of a dim and evil past—who must now be watching this cottage as bloodlustful devotees watch a shrine violated, burst upon my mind. I peopled the still blackness with lurking assassins, armed with the murderous knowledge of by-gone centuries, armed with invisible weapons which struck down from afar, supernaturally.
 
I glanced toward the corner of the room where the safe stood, reliquary of a worthless thing for which much blood had been spilled.
 
Then sounded footsteps along the avenue, and my fear whispered that they were not those of Bristol but of one who had murdered him, and who came guilefully, to murder me!
 
I snatched the revolver from my pocket and crossed the darkened room. Just to the right of one of the French windows I stood looking out across the loggia to the end of the avenue. The night was a bright one, and the room was flooded with a reflected mystic light, but outside the moon paved the avenue with pearl, and through the trees I saw a figure approaching.
 
Was it Bristol? It had his build, it had his gait; but my fears remained. Then the figure crossed the patch of shrubbery and stepped on to the loggia.
 
"Mr. Cavanagh!"
 
I laughed dryly at my own cowardice, but my heart was still beating abnormally.
 
"Here I am, Bristol, in a ghastly funk!"
 
"I don't wonder! They may be on us any time now. All's well at the gate, but Morris says he heard, or thought he heard something at the side of the chapel opposite, a while ago."
 
"Wind in the bushes?"
 
"It may have been; but he says there was no breeze at the time."
 
We resumed our seats.
 
"Bristol," I said, "now that the danger grows imminent, doesn't it seem to you foolhardy for us thus to expose ourselves?"
 
"Perhaps it is," he agreed; "but how otherwise are we likely to learn what happened to Marden and West?"
 
"The enemy may adopt different measures to-night."
 
"I think not. Our dispositions are the same, and I credit them with cunning enough to know it. At the same time I credit ourselves with having kept the existence of the steel traps completely secret. They will assume (so I've reasoned) that we intend to rely entirely upon our superior vigilance, therefore they will try the same game as last night."
 
Silence fell.
 
The moon rays, creeping around from the right of the avenue, crossing the shrubbery and encroaching upon the low wall of the loggia, now flooded its floor. Against the silvern light, Bris............