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."