Bristol and Mostyn walked on then; but I stood just within the doorway, intently, breathlessly watching an old man wearing an out-of-date Inverness coat and a soft felt hat.  He had a gray beard and moustache, and long, untidy hair, walked with a stoop, and in short was no unusual type of Visitor to that institution.

But it seemed to me, and the closer I watched him the more convinced I became, that this was no optical illusion, that a faint luminosity, a sort of elfin light, played eerily about his head!

As Bristol and Mostyn approached the case the old man began to walk toward me and in the direction of the door.  The idea flashed through my mind that it might be Hassan of Aleppo himself, Hassan who had predicted that the stolen slipper should that day be returned to the Museum!

Then he came abreast of me, passed me, and I felt that my surmise had been wrong.  I saw Bristol, from farther up the room, turn and look back.  Something attracted his trained eye, I suppose, which was not perceptible to me.  But he suddenly came striding along.  Obviously he was pursuing the old man, who was just about to leave the apartment.  Seeing that the latter had reached the doorway, Bristol began to run.

The old man turned; and amid a chorus of exclamations from the astonished spectators, Bristol sprang upon him!

How it all came about I cannot say, cannot hope to describe; but there was a short, sharp scuffle, the crack of a well-directed blow . . . and Bristol was rolling on his back, the old man, hatless, was racing up the Assyrian Room, and everyone in the place seemed to be shouting at once!

Bristol, with blood streaming from his face, staggered to his feet, clutching at me for support.

“After him, Mr. Cavanagh!” he cried hoarsely.  “It’s your turn to-day!  After him!  That’s Earl Dexter!”

Mostyn waited for no more, but went running quickly through the Assyrian Room.  I may mention here that at the head of the stairs he found the caped Inverness which had served to conceal Dexter’s mutilated arm, and later, behind a piece of statuary, a wig and a very ingenious false beard and moustache were discovered.  But of The Stetson Man there was no trace.  His brief start had enabled him to make good his escape.

As Mostyn went off, and a group of visitors flocked in our direction, Bristol, who had been badly shaken by the blow, turned to them.

“You will please all leave the Burton Room immediately,” he said.

Looks of surprise greeted his words; but with his handkerchief raised to his face, he peremptorily repeated them.  The official note in his voice was readily to be detected; and the wonder-stricken group departed with many a backward glance.

As the last left the Burton Room, Bristol pointed, with a rather shaky finger, at the soft felt hat which lay at his feet.  It had formed part of Dexter’s disguise.  Close beside it lay another object which had evidently fallen from the hat—­a dull red thing lying on the polished parquet flooring.