impression as I opened the door was that a fire had broken out,
for the room was so filled with smoke that the light of the lamp upon
the table was blurred by it. As I entered, however, my fears were set at
rest, for it was the acrid fumes of strong coarse tobacco which took me
by the throat and set me coughing. Through the haze I had a vague vision
of Holmes in his dressing-gown coiled up in an armchair with his black
clay pipe between his lips. Several rolls of paper lay around him.

"Caught cold, Watson?" said he.

"No, it's this poisonous atmosphere."

"I suppose it is pretty thick, now that you mention it."

"Thick! It is intolerable."

"Open the window, then! You have been at your club all day, I perceive."

"My dear Holmes!"

"Am I right?"

"Certainly, but how?"

He laughed at my bewildered expression. "There is a delightful freshness
about you, Watson, which makes it a pleasure to exercise any small
powers which I possess at your expense. A gentleman goes forth on a
showery and miry day. He returns immaculate in the evening with the
gloss still on his hat and his boots. He has been a fixture therefore
all day. He is not a man with intimate friends. Where, then, could he
have been? Is it not obvious?"

"Well, it is rather obvious."

"The world is full of obvious things which nobody by any chance ever
observes. Where do you think that I have been?"

"A fixture also."

"On the contrary, I have been to Devonshire."

"In spirit?"

"Exactly. My body has remained in this armchair and has, I regret
to observe, consumed in my absence two large pots of coffee and an
incredible amount of tobacco. After you left I sent down to Stamford's
for the Ordnance map of this portion of the moor, and my spirit has
hovered over it all day. I flatter myself that I could find my way
about."

"A large-scale map, I presume?"

"Very large."

He unrolled one section and held it over his knee. "Here you have the
particular district which concerns us. That is Baskerville Hall in the
middle."

"With a wood round it?"

"Exactly. I fancy the yew alley, though not marked under that name, must
stretch along this line, with the moor, as you perceive, upon the right
of it. This small clump of buildings here is the hamlet of Grimpen,
where our friend Dr. Mortimer has his headquarters. Within a radius of
five miles there are, as you see, only a very few scattered dwellings.
Here is Lafter Hall, which was mentioned in the na