ous things. We could not smoke and must converse only in
whispers; and so the night wore on until I began to think that our
watch would be dully uneventful.

"Our big chance," whispered Mostyn, "is in the fact that any day
may change the conditions. They can't afford to wait."

He ceased abruptly, grasping my arm. From somewhere, somewhere
outside the building, we all three had heard a soft whistle. A
moment of tense listening followed.

"If only we could have had the place surrounded," whispered Bristol--"but
it was impossible, of course."

A faint grating noise echoed through the lofty Burton Room. Bristol
slipped past me in the semi-gloom, and gently opened the
communicating door a few inches.

A-tiptoe, I joined him, and craning across his shoulder saw a strange
and wonderful thing.

The newly glazed east window again was shattered with a booming
crash! The yellow blind was thrust aside. A long something reached
out toward the broken case. There was a sort of fumbling sound, and
paralyzed with the wonder of it--for the window, remember, was
thirty feet from the ground--I stood frozen to my post.

Not so Bristol. As the weird tentacle (or more exactly it reminded
me of a gigantic crab's claw) touched the case, the Inspector leapt
forward. A white beam from his electric torch cut through to the
broken cabinet.

The thing was withdrawn ... and with it went the slipper of the
Prophet.

"Raise the blinds!" cried Bristol. "Mr. Cavanagh! Mr. Mostyn!
We must not let them give us the slip!"

I got up the blind of the nearer window as Bristol raised the other.
Not a living thing was in sight from either!

Mostyn was beside me, his hand resting on my shoulder. I noted how
he trembled. Bristol turned and looked back at us. The light from
his pocket torch flashed upon the curator's face; and I have never
seen such an expression of horrified amazement as that which it
wore. Faintly, I could hear the constable racing up the steps from
the hall.

Ideas of the supernatural came to us all, I know; when, with a
scuffling sound not unlike that of a rat in a ceiling, something moved
above us!

"Damn my thick head!" roared Bristol, furiously. "He's on the roof!
It's flat as a floor and there's enough ivy alongside the water-spout
on your house adjoining, Mr. Mostyn, to afford foothold to an
invading army!"

He plunged off toward the open door, and I heard him racing down
the Assyrian Room.

"He had