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,” Bristol whispered to me, “at the exact time when the moonlight shone through the hole in the westerly blind on to the case. If they come to-night, and I am quite expecting them, they will have to dispense with that assistance; but they know by experience where to reach the case.”
“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.