"the american gentleman has just gone out, sir," said the sergeant at the door.

i nodded grimly and raced down the steps. despite my half-formed desire that the slipper should be recovered by those to whom properly it belonged, i experienced at times a curious interest in its welfare. i cannot explain this. across the hall in front of me i saw earl dexter passing out of the museum. i followed him through into kingsway and thence to fleet street. he sauntered easily along, a nonchalant gray figure. i had begun to think that he was bound for his hotel and that i was wasting my time when he turned sharply into quiet salisbury square; it was almost deserted.

my heart leapt into my mouth with a presentiment of what was coming as i saw an elegant and beautifully dressed woman sauntering along in front of us on the far side.

was it that i detected something familiar in her carriage, in the poise of her head—something that reminded me of former unforgettable encounters; encounters which without exception had presaged attempts upon the slipper of the prophet? or was it that i recollected how dexter had booked two passages to america? i cannot say, but i felt my heart leap; i knew beyond any possibility of doubt that this meeting in salisbury square marked the opening of a new chapter in the history of the slipper.

dexter slipped his arm within that of the girl in front of him and they paced slowly forward in earnest conversation. i suppose my action was very amateurish and very poor detective work; but regardless of discovery i crossed the road and passed close by the pair.

i am certain that dexter was speaking as i came up, but, well out of earshot, his voice was suddenly arrested. his companion turned and looked at me.

i was prepared for it, yet was thrilled electrically by the flashing glance of the violet eyes—for it was she—the beautiful harbinger of calamities!

my brain was in a whirl; complication piled itself upon complication; yet in the heart of all this bewilderment i thought i could detect the key of the labyrinth, but at the time my ideas were in disorder, for the violet eyes were not lowered but fixed upon me in cold scorn.

i knew myself helpless, and bending my head with conscious embarrassment i passed on hurriedly.

i had work to do in plenty, but i could not apply my mind to it; and now, although the obvious and sensible thing was to go about my business, i wandered on aimlessly, my brain employed with a hundred idle conjectures and the query, "where have i seen the stetson man?" seeming to beat, like a tattoo, in my brain. there was something magnetic about the accursed slipper, for without knowing by what route i had arrived there, i found myself in great orchard street and close under the walls of the british antiquarian museum. then i was effectually aroused from my reverie.

two men, both tall, stood in the shadow of a doorway on the opposite side of the street, staring intently up at the museum windows. it was a tropically hot afternoon and they stood in deepest shadow. no one else was in orchard street—that odd little backwater—at the time, and they stood gazing upward intently and gave me not even a passing glance.

but i knew one for the oriental visitor of the morning, and despite broad noonday and the hum of busy london about me, my blood seemed to turn to water. i stood rooted to the spot, held there by a most surprising horror.

for the gray-bearded figure of the other watcher was one i could never forget; its benignity was associated with the most horrible hours of my life, with deeds so dreadful that recollection to this day sometimes breaks my sleep, arousing me in the still watches, bathed in a cold sweat of fear.

it was hassan of aleppo!

if he saw me, if either of them saw me, i cannot say. what i should have done, what i might have done it is useless to speak of here—for i did nothing. inert, thralled by the presence of that eerie, dreadful being, i watched them leave the shadow of the doorway and pace slowly on with their dignified eastern gait.

then, knowing how i had failed in my plain duty to my fellow-men—how, finding a serpent in my path, i had hesitated to crush it, had weakly succumbed to its uncanny fascination—i made my way round to the door of the museum.