Mostyn sprang up in bed, drew on a dressing-gown, and took from the small safe at his bed-head the Museum keys and a loaded revolver.  A somewhat dishevelled figure, pale and wild-eyed, he made his way through the private door and into the ghostly precincts of the Museum.  He did not hesitate, but ascended the stairs and unlocked the door of the Assyrian gallery.

Along its ghostly aisles he passed, and before the door which gave admittance to the Burton Room paused, fumbling a moment for the key.

Inside the room something was moving!

Mostyn was keenly alarmed; he knew that he must enter at once or never.  He inserted the key in the lock, swung open the heavy door, stepped through and closed it behind him.  He was a man of tremendous moral courage, for now,—­alone in the apartment which harboured the uncanny relic, alone in the discharge of his duty, he stood with his back to the door trembling slightly, but with the idea of retreat finding no place in his mind.

One side of the room lay in blackest darkness; through the furthermost window of the other a faint yellowed luminance (the moonlight through the blind) spread upon the polished parquet flooring.  But that which held the curator spell-bound—­that which momentarily quickened into life the latent superstition, common to all mankind, was a beam of cold light which poured its effulgence fully upon the case containing the Prophet’s slipper!  Where the other exhibits lay either in utter darkness or semi-darkness this one it seemed was supernaturally picked out by this lunar searchlight!

It was ghostly-unnerving; but, the first dread of it passed, Mostyn recalled how during the day a hole inexplicably had been cut in that blind; he recalled that it had not been mended, but that the damaged blind had merely been rolled up again.

And as a dawning perception of the truth came to him, as falteringly he advanced a step toward the mystic beam, he saw that one side of the case had been shattered—­he saw the broken glass upon the floor; and in the dense shadow behind and under the beam of light, vaguely he saw a dull red object.

It moved—­it seemed to live!  It moved away from the case and in the direction of the eastern windows.

“My God!” whispered Mostyn; “it’s the Prophet’s slipper!”

And wildly, blindly, he fired down the room.  Later he knew that he had fired in panic, for nothing human was or could be in the place; yet his shot was not without effect.  In the instant of its flash, something struck sharply against the dimly seen blind of one of the east windows; he heard the crash of broken glass.

He leapt to the switch and flooded the room with light.  A fear of what it might hold possessed him, and he turned instantly.

Hard by the fragments of broken glass upon the floor and midway between the case and the first easterly window lay the slipper.  A bell was ringing somewhere.  His shot probably had aroused the attention of the policeman.  Someone was clamouring upon the door of the Museum, too.  Mostyn raced forward and raised the blind —­that toward which the slipper had seemed to move.