occasional ten-pound note sent to him by
devious methods, he has once or twice given me advance information
which has been of value--that highest value which anticipates and
prevents rather than avenges crime. I cannot doubt that, if we had the
cipher, we should find that this communication is of the nature that I
indicate."

Again Holmes flattened out the paper upon his unused plate. I rose and,
leaning over him, stared down at the curious inscription, which ran as
follows:

534 C2 13 127 36 31 4 17 21 41

DOUGLAS 109 293 5 37 BIRLSTONE

26 BIRLSTONE 9 47 171

"What do you make of it, Holmes?"

"It is obviously an attempt to convey secret information."

"But what is the use of a cipher message without the cipher?"

"In this instance, none at all."

"Why do you say 'in this instance'?"

"Because there are many ciphers which I would read as easily as I do
the apocrypha of the agony column: such crude devices amuse the
intelligence without fatiguing it. But this is different. It is clearly
a reference to the words in a page of some book. Until I am told which
page and which book I am powerless."

"But why 'Douglas' and 'Birlstone'?"

"Clearly because those are words which were not contained in the page
in question."

"Then why has he not indicated the book?"

"Your native shrewdness, my dear Watson, that innate cunning which is
the delight of your friends, would surely prevent you from inclosing
cipher and message in the same envelope. Should it miscarry, you are
undone. As it is, both have to go wrong before any harm comes from it.
Our second post is now overdue, and I shall be surprised if it does not
bring us either a further letter of explanation, or, as is more
probable, the very volume to which these figures refer."

Holmes's calculation was fulfilled within a very few minutes by the
appearance of Billy, the page, with the very letter which we were
expecting.

"The same writing," remarked Holmes, as he opened the envelope, "and
actually signed," he added in an exultant voice as he unfolded the
epistle. "Come, we are getting on, Watson." His brow clouded, however,
as he glanced over the contents.

"Dear me, this is very disappointing! I fear, Watson, that all our
expectations come to nothing. I trust that the man Porlock will come to
no harm.

"DEAR MR. HOLMES [he says]:

"I will go no further in this matter. It is too dangerous--