employer. A private detective may, and usually does, become
possessed of information even more valuable to the person who
is being watched than to the person to whom he owes his
allegiance. Unreliable rascals constantly sell out to the
other side and play both ends against the middle. In this
they resemble some of the famous diplomatic agents of history.
And police detectives employed to run down criminals and
protect society have been known instead to act as stalls for
bank burglars and (for a consideration) to assist them to
dispose of their booty and protect them from arrest and
capture. It has repeatedly happened that reliable private
detectives have discovered that the police employed upon the
same case have in reality been tipping off the criminals as to
what was being done and coaching them as to their conduct. Of
course the natural jealousy existing between official and
unofficial agents of the law leads to many unfounded
accusations of this character, but, on the other hand, the
fact that much of the most effective police work is done by
employing professional criminals to secure information and act
as stool-pigeons often results in a definite understanding
that the latter shall be themselves protected in the quiet
enjoyment of their labors. The relations of the regular
police to crime, however, and the general subject of police
graft have little place in a chapter of this character.

The first question that usually arises is whether a detective
shall or shall not be employed at all in any particular case.
Usually the most important thing is to find out what the real
character, past, and associations of some particular
individual may be. Well-established detective agencies with