It was half-past five before Holmes returned. He was bright,
eager, and in excellent spirits,--a mood which in his case
alternated with fits of the blackest depression.

"There is no great mystery in this matter," he said, taking the
cup of tea which I had poured out for him. "The facts appear to
admit of only one explanation."

"What! you have solved it already?"

"Well, that would be too much to say. I have discovered a
suggestive fact, that is all. It is, however, VERY suggestive.
The details are still to be added. I have just found, on
consulting the back files of the Times, that Major Sholto, of
Upper Norword, late of the 34th Bombay Infantry, died upon the
28th of April, 1882."

"I may be very obtuse, Holmes, but I fail to see what this
suggests."

"No? You surprise me. Look at it in this way, then. Captain
Morstan disappears. The only person in London whom he could have
visited is Major Sholto. Major Sholto denies having heard that
he was in London. Four years later Sholto dies. WITHIN A WEEK
OF HIS DEATH Captain Morstan's daughter receives a valuable
present, which is repeated from year to year, and now culminates
in a letter which describes her as a wronged woman. What wrong
can it refer to except this deprivation of her father? And why
should the presents begin immediately after Sholto's death,
unless it is that Sholto's heir knows something of the mystery
and desires to make compensation? Have you any alternative
theory which will meet the facts?"

"But what a strange compensation! And how strangely made! Why,
too, should he write a letter now, rather than six years ago?
Again, the letter speaks of giving her justice. What justice can
she have? It is too much to suppose that her father is still
alive. There is no other injustice in her case that you know
of."

"There are difficulties; there are certainly difficulties," said
Sherlock Holmes, pensively. "But our expedition of to-night will
solve them all. Ah, here is a four-wheeler, and Miss Morstan is
inside. Are you all ready? Then we had better go down, for it
is a little past the hour."

I picked up my hat and my heaviest stick, but I observed that
Holmes took his revolver from his drawer and slipped it into his
pocket. It was clear that he thought that our night's work might
be a serious one.

Miss Morstan was muffled in a dark cloak, and her sensitive face
was composed, but pale. She must have been more than woman if
she did not feel some uneasiness at the strange enterprise upon
which we were embarking, yet her self-control was perfect, and
she readily answered the few additional questions which Sherlock
Holmes put to her.

"Major Sholto was a very particular friend of papa's," she said.
"His letters were full of allusions to the major. He and papa
were in command of the troops at the Andaman Islands, so they
were thrown a great deal together. By the way, a curious paper
was found in papa's desk which no one could understand. I don't
suppose that it is of the slightest importance, but I thought you
might care to see it, so I brought it with me. It is here."

Holmes unfolded the paper carefully and smoothed it out upon his
knee. He then very methodically examined it all over with his
double lens.

"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
diffused light which threw a feeble circular glimmer upon the
slimy pavement. The yellow glare from the shop-windows streamed
out into the steamy, vaporous air, and threw a murky, shifting
radiance across the crowded thoroughfare. There was, to my mind,
something eerie and ghost-like in the endless procession of faces
which flitted across these narrow bars of light,--sad faces and
glad, haggard and merry. Like all human kind, they flitted from
the gloom into the light, and so back into the gloom once more.
I am not subject to impressions, but the dull, heavy evening,
with the strange business upon which we were engaged, combined to
make me nervous and depressed. I could see from Miss Morstan's
manner that she was suffering from the same feeling. Holmes
alone could rise superior to petty influences. He held his open
note-book upon his knee, and from time to time he jotted down
figures and memoranda in the light of his pocket-lantern.

At the Lyceum Theatre the crowds were already thick at the side-
entrances. In front a continuous stream of hansoms and four-
wheelers were rattling up, discharging their cargoes of shirt-
fronted men and beshawled, bediamonded women. We had hardly
reached the third pillar, which was our rendezvous, before a
small, dark, brisk man in the dress of a coachman accosted us.

"Are you the parties who come with Miss Morstan?" he asked.

"I am Miss Morstan, and these two gentlemen are my friends," said
she.

He bent a pair of wonderfully penetrating and questioning eyes
upon us. "You will excuse me, miss," he said with a certain
dogged manner, "but I was to ask you to give me your word that
neither of your companions is a police-officer."

"I give you my word on that," she answered.

He gave a shrill whistle, on which a street Arab led across a
four-wheeler and opened the door. The man who had addressed us
mounted to the box, while we took our places inside. We had
hardly done so before the driver whipped up his horse, and we
plunged away at a furious pace through the foggy streets.

The situation was a curious one. We were driving to an unknown
place, on an unknown errand. Yet our invitation was either a
complete hoax,--which was an inconceivable hypothesis,--or else
we had good reason to think that important issues might hang upon
our journey. Miss Morstan's demeanor was as resolute and
collected as ever. I endeavored to cheer and amuse her by
reminiscences of my adventures in Afghanistan; but, to tell the
truth, I was myself so excited at our situation and so curious as
to our destination that my stories were slightly involved. To
this day she declares that I told her one moving anecdote as to
how a musket looked into my tent at the dead of night, and how I
fired a double-barrelled tiger cub at it. At first I had some
idea as to the direction in which we were driving; but soon, what
with our pace, the fog, and my own limited knowledge of London, I
lost my bearings, and knew nothing, save that we seemed to be
going a very long way. Sherlock Holmes was never at fault,
however, and he muttered the names as the cab rattled through
squares and in and out by tortuous by-streets.

"Rochester Row," said he. "Now Vincent Square. Now we come out
on the Vauxhall Bridge Road. We are making for the Surrey side,
apparently. Yes, I thought so. Now we are on the bridge. You
can catch glimpses of the river."

We did indeed get a fleeting view of a stretch of the Thames with
the lamps shining upon the broad, silent water; but our cab
dashed on, and was soon involved in a labyrinth of streets upon
the other side.

"Wordsworth Road," said my companion. "Priory Road. Lark Hall
Lane. Stockwell Place. Robert Street. Cold Harbor Lane. Our
quest does not appear to take us to very fashionable regions."

We had, indeed, reached a questionable and forbidding
neighborhood. Long lines of dull brick houses were only relieved
by the coarse glare and tawdry brilliancy of public houses at the
corner. Then came rows of two-storied villas each with a
fronting of miniature garden, and then again interminable lines
of new staring brick buildings,--the monster tentacles which the
giant city was throwing out into the country. At last the cab
drew up at the third house in a new terrace. None of the other
houses were inhabited, and that at which we stopped was as dark
as its neighbors, save for a single glimmer in the kitchen
window. On our knocking, however, the door was instantly thrown
open by a Hindoo servant clad in a yellow turban, white loose-
fitting clothes, and a yellow sash. There was something
strangely incongruous in this Oriental figure framed in the
commonplace door-way of a third-rate suburban dwelling-house.

"The Sahib awaits you," said he, and even as he spoke there came
a high piping voice from some inner room. "Show them in to me,
khitmutgar," it cried. "Show them straight in to me."