"Despite our precautions," I said, "they will almost certainly
know that a watch is being kept."

"They may or they may not," replied Bristol. "Either way I'm
disposed to think there will be another attempt. Their mysterious
method is so rapid that they can afford to take chances."

This was not my first night vigil since I had become in a sense the
custodian of the relic, but it was quite the most dreary. Amid the
tomb-like objects about us we seemed two puny mortals toying with
stupendous 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.