"Who knew that you were going to the Northumberland Hotel?" asked
Holmes, glancing keenly across at our visitor.

"No one could have known. We only decided after I met Dr. Mortimer."

"But Dr. Mortimer was no doubt already stopping there?"

"No, I had been staying with a friend," said the doctor.

"There was no possible indication that we intended to go to this
hotel."

"Hum! Someone seems to be very deeply interested in your movements."
Out of the envelope he took a half-sheet of foolscap paper folded
into four. This he opened and spread flat upon the table. Across
the middle of it a single sentence had been formed by the expedient
of pasting printed words upon it. It ran:

As you value your life or your reason keep away from the moor.

The word "moor" only was printed in ink.

"Now," said Sir Henry Baskerville, "perhaps you will tell me, Mr.
Holmes, what in thunder is the meaning of that, and who it is
that takes so much interest in my affairs?"

"What do you make of it, Dr. Mortimer? You must allow that there
is nothing supernatural about this, at any rate?"