with his duty, a man keeps on
good terms with those criminals he knows. It is a point of policy. They
know that the average detective does not wish them harm. If he has to
arrest them they know he will be scrupulously fair when it comes to
giving evidence. Often a detective will help a man out of his own pocket
when he knows that a case is really a necessitous one. He has no animus
against any person he arrests. His duty is merely to place in safe
custody the person he believes to be responsible for a breach of the
law. Conviction or acquittal matters nothing to him after that. He has
done his duty.

A wide knowledge of human nature is necessary to his calling, and he
never forgets that the power of a police officer has its limitations. A
man who brings discredit or ridicule on the department has a short-lived
official life.

There is another part of the Criminal Investigation Department which has
duties entirely distinct from that of the main body of detectives. That
is the Special Branch, under Superintendent Quinn, M.V.O.--a section
which, with the war, has suddenly become of great importance, for it has
now largely to do with the spy peril. Of its methods and organisation
little can be said, for obvious reasons.

In ordinary times it concerns itself solely with the protection of high
personages, from the King and Queen and Cabinet Ministers to
distinguished foreign visitors. The Special Branch in the days of
suffragette outrages was the chief foe of the vote-seekers. It deals,
too, with all political offences which need investigation.

There is a special squad of officers who deal with the white slave
traffic. These are assisted by a lady appointed by the Home Office. She
makes enquiries from women and children where victims might be reluctant
to confide in a man, and has other similar duties.

The department is practically self-contained, working side by side with
the uniform branch under its own officers. The point of contact is at
superintendents of divisions, who exercise a supervising control.

CHAPTER VII.

THE CROOKS' CLEARING-HOUSE.

Many high authorities have argued that the best way to prevent crime is
to keep all known criminals under lock and key, as we do lunatics. The
theory may be right or wrong, but it is not yet possible to put it into
practice.

So Scotland Yard does the next best thing, and exercises a quiet,
unwearying, persistent surveillance on those hundreds of persons who a