The day that followed was one of the hottest which we experienced during the heat wave. It was a day crowded with happenings. The Burton Room was closed to the public, whilst a glazier worked upon the broken east window and a new blind was fitted to the west. Behind the workmen, guarded by a watchful commissionaire, yawned the shattered case containing the slipper.  
I wondered if the visitors to the other rooms of the Museum realized, as I realized, that despite the blazing sunlight of tropical London, the shadow of Hassan of Aleppo lay starkly on that haunted building?
 
At about eleven o'clock, as I hurried along the Strand, I almost collided with the girl of the violet eyes! She turned and ran like the wind down Arundel Street, whilst I stood at the corner staring after her in blank amazement, as did other passers-by; for a man cannot with dignity race headlong after a pretty woman down a public thoroughfare!
 
My mystification grew hourly deeper; and Bristol wallowed in perplexities.
 
"It's the most horrible and confusing case," he said to me when I joined him at the Museum, "that the Yard has ever had to handle. It bristles with outrages and murders. God knows where it will all end. I've had London scoured for a clue to the whereabouts of Hassan and Company and drawn absolutely blank! Then there's Earl Dexter. Where does he come in? For once in a way he's living in hiding. I can't find his headquarters. I've been thinking—"
 
He drew me aside into the small gallery which runs parallel with the Assyrian Room.
 
"Dexter has booked two passages in the Oceanic. Who is his companion?"
 
I wondered, I had wondered more than once, if his companion were my beautiful violet-eyed acquaintance. A scruple—perhaps an absurd scruple—hitherto had kept me silent respecting her, but now I determined to take Bristol fully into my confidence. A conviction was growing upon me that she and Earl Dexter together represented that third party whose existence we had long suspected. Whether they operated separately or on behalf of the Moslems (of which arrangement I could not conceive) remained to be seen. I was about to voice my doubts and suspicions when Bristol went on hurriedly—
 
"I have thoroughly examined the Burton Room, and considering that the windows are thirty feet from the ground, that there is no sign of a ladder having stood upon the lawn, and that the iron bars are quite intact, it doesn't look humanly possible for any one to have been in the room last night prior to Mostyn's arrival!"
 
"One of the dwarfs—"
 
"Not even one of the dwarfs," said Bristol, "could have passed between those iron bars!"
 
"But there was blood on the window!"
 
"I know there was, and human blood. It's been examined!"
 
He stared at me fixedly. The thing was unspeakably uncanny.
 
"To-night," he went on, "I am remaining in here"—nodding toward the Assyrian Room—"and I have so arranged it that no mortal being can possibly know I am here. Mostyn is staying, and you can stay, too, if you care to. Owing to Professor Deeping's will you are badly involved in the beastly business, and I have no doubt you are keen to see it through."
 
"I am," I admitted, "and the end I look for and hope for is the recovery of the slipper by its murderous owners!"
 
"I am with you," said Bristol. "It's just a point of honour; but I should be glad to make them a present of it. We're ostentatiously placing a constable on duty in the hallway to-night—largely as a blind. It will appear that we're taking no other additional precautions."
 
He hurried off to make arrangements for my joining him in his watch, and thus again I lost my opportunity of confiding in him regarding the mysterious girl.
 
I half anticipated, though I cannot imagine why, that Earl Dexter would put in an appearance, during the day. He did not do so, however, for Bristol had put a constable on the door who was well acquainted with the appearance of The Stetson Man. The inspector, in the course of his investigations, had come upon what might have been a clue, but what was at best a confusing one. Close by the wall of the curator's house and lying on the gravel path he had found a part of a gold cuff link. It was of American manufacture.
 
Upon such slender evidence we could not justly assume that it pointed to the presence of Dexter on the night of the attempted robbery, but it served to complicate a matter already sufficiently involved.
 
In pursuance of Bristol's plan, I concealed myself that evening just before the closing of the Museum doors, in a recess behind a heavy piece of Babylonian sculpture. Bristol was similarly concealed in another part of the room, and Mostyn joined us later.
 
The Museum was closed; and so far as evidence went the authorities had relied again upon the bolts and bars hitherto considered impregnable, and upon the constable in the hall. The broken window was mended, the cut blind replaced, and within, in its shattered case, reposed the slipper of the Prophet.
 
All the blinds being lowered, the Assyrian Room was a place of gloom, yellowed on the western side by the moonlight through the blind. The door communicating with the Burton Room was closed but not fastened.
 
"They operated last night," Bristo............