was that of a spy pure and simple.

Another highly specialized class of detectives is that engaged
in police and banking work, who by experience (or even origin)
have a wide and intimate acquaintance with criminals of
various sorts, and by their familiarity with the latters'
whereabouts, associates, work, and methods are able to
recognize and run down the perpetrators of particular crimes.

Thus, for example, there are men in the detective bureau of
New York City who know by name, and perhaps have a speaking
acquaintance with, a large number of the pick-pockets and
burglars of the East Side. They know their haunts and their
ties of friendship or marriage. When any particular job is
pulled off they have a pretty shrewd idea of who is
responsible for it and lay their plans accordingly. If
necessary, they run in the whole gang and put each of them
through a course of interrogation, accusation, and browbeating
until some one breaks down or makes a slip that involves him
in a tangle. These men are special policemen whose knowledge
makes them detectives by courtesy. But their work does not
involve any particular superiority or quickness of intellect
--the quality which we are wont to associate with the
detection of crime.

Now, if the ordinary householder finds that his wife's
necklace has mysteriously disappeared, his first impulse is to
send for a detective of some sort or other. In general, he
might just as well send for his mother-in-law. Of course, the
police can and will watch the pawnshops for the missing