ned the piece of paper in his
pocket-book with a new and keen interest. There was no doubt about it,
the mark on the dirty blank paper was undoubtedly the Treasury
watermark. But how came such a mark, designed exclusively for the
protection of the Treasury against bank-note forgeries, to appear on a
dirty scrap of paper?

As he stood there, turning the bit of paper over and over, in his hand,
puzzling over the problem, the solution flashed into his mind--a
solution so simple, yet, withal, so remarkable, that he hesitated to
believe it possible. But a further examination of the paper removed his
doubts. Chance had placed in his hands another clue, and the most
important he had yet discovered, to help him in the elucidation of the
mystery of the murder of Roger Glenthorpe. But to verify that clue it
would be necessary for him to descend the pit.

CHAPTER XXI

An orange crescent of a waning moon was sinking in a black sky as Colwyn
let himself quietly out of the door and took his way up to the rise. But
the darkness of the night was fading fast before the grey dawn of the
coming day, and in the marshes below the birds were beginning to stir
and call among the reeds.

Colwyn waited for the first light of dawn before attempting the descent
of the pit. His plan was to climb down by the creepers as far as they
went, and descend the remainder of the distance by the rope, which he
would fasten to one of the shrubs growing in the interior. He realised
that his chances of success depended on the slope of the pit and the
depth to which the shrubs grew, but the attempt was well worth making.
Assistance would have made the task much easier, but publicity was the
thing Colwyn desired most to avoid at that stage of his investigations.
There would be time enough to consider the question of seeking help if
he failed in his individual effort.

He made his plans carefully before commencing the descent. He first
tested a rope he had found in the lumber room of the inn; it was thin
but strong and capable of bearing the weight of a heavier man than
himself. The rope was not more than fifteen feet in length, but if the
hardy climbing plants which lined the sides of the pit were capable of
supporting him ten or twelve feet down, that length should be sufficient
for his purpose. Having tested the rope and coiled it, he slipped it
into the right-hand pocket of his coat with one end hanging out. Next he
opened his knife, and placed it