It alone has the proper plant and equipment for the work.

In an emergency, organization counts more than anything else.

Where time is of the essence, the individual has no opportunity to hire his own men or start an organization of his own.

But if the matter is one where there is plenty of leisure to act, you can usually do your own detective work better and cheaper than any one else.
Regarding the work of the detective as a spy (which probably constitutes seventy-five per cent of his employment to-day), few persons realize how widely such services are being utilized.

The insignificant old Irishwoman who stumbles against you in the department store is possibly watching with her cloudy but eagle eye for shoplifters.