Baskerville
has been very closely shadowed by someone since he has been in
town. How else could it be known so quickly that it was the
Northumberland Hotel which he had chosen? If they had followed
him the first day I argued that they would follow him also the
second. You may have observed that I twice strolled over to the
window while Dr. Mortimer was reading his legend."

"Yes, I remember."

"I was looking out for loiterers in the street, but I saw none.
We are dealing with a clever man, Watson. This matter cuts very
deep, and though I have not finally made up my mind whether it is
a benevolent or a malevolent agency which is in touch with us, I
am conscious always of power and design. When our friends left I
at once followed them in the hopes of marking down their
invisible attendant. So wily was he that he had not trusted
himself upon foot, but he had availed himself of a cab so that he
could loiter behind or dash past them and so escape their notice.
His method had the additional advantage that if they were to take
a cab he was all ready to follow them. It has, however, one
obvious disadvantage."

"It puts him in the power of the cabman."

"Exactly."

"What a pity we did not get the number!"

"My dear Watson, clumsy as I have been, you surely do not
seriously imagine that I neglected to get the number? No. 2704 is
our man. But that is no use to us for the moment."

"I fail to see how you could have done more."

"On observing the cab I should have instantly turned and walked
in the other direction. I should then at my leisure have hired a
second cab and followed the first at a respectful distance, or,
better still, have driven to the Northumberland Hotel and waited
there. When our unknown had followed Baskerville home we should
have had the opportunity of playing his own game upon himself and
seeing where he made for. As it is, by an indiscreet eagerness,
which was taken advantage of with extraordinary quickness and
energy by our opponent, we have betrayed ourselves and lost our
man."

We had been sauntering slowly down Regent Street during this
conversation, and Dr. Mortimer, with his companion, had long
vanished in front of us.

"There is no object in our following them," said Holmes. "The
shadow has departed and will not return. We must see what further
cards we have in our hands and play them with decision. Could you
swear to that man's face within the cab?"

"I could swear only to the beard."