"It is paper of native Indian manufacture," he remarked. "It has
at some time been pinned to a board. The diagram upon it appears
to be a plan of part of a large building with numerous halls,
corridors, and passages. At one point is a small cross done in
red ink, and above it is '3.37 from left,' in faded pencil-
writing. In the left-hand corner is a curious hieroglyphic like
four crosses in a line with their arms touching. Beside it is
written, in very rough and coarse characters, 'The sign of the
four,--Jonathan Small, Mahomet Singh, Abdullah Khan, Dost Akbar.'
No, I confess that I do not see how this bears upon the matter.
Yet it is evidently a document of importance. It has been kept
carefully in a pocket-book; for the one side is as clean as the
other."

"It was in his pocket-book that we found it."

"Preserve it carefully, then, Miss Morstan, for it may prove to
be of use to us. I begin to suspect that this matter may turn
out to be much deeper and more subtle than I at first supposed.
I must reconsider my ideas." He leaned back in the cab, and I
could see by his drawn brow and his vacant eye that he was
thinking intently. Miss Morstan and I chatted in an undertone
about our present expedition and its possible outcome, but our
companion maintained his impenetrable reserve until the end of
our journey.

It was a September evening, and not yet seven o'clock, but the
day had been a dreary one, and a dense drizzly fog lay low upon
the great city. Mud-colored clouds drooped sadly over the muddy
streets. Down the Strand the lamps were but misty splotches of