Having been connected for many years with two of the largest and most successful private detective agencies in this country, both as an operator and as an official, and having been requested to outline briefly and concisely the most modern and up-to-date methods employed by leading detectives and private detective agencies of today, I shall confine myself in these pages to facts and a few personal experiences. I will endeavor to show that any person possessed of average intelligence, and who will use good common sense, can become a successful detective, regardless of his present or previous occupation.

This country today stands in need of more and better detectives than ever before in its history, and if one be inclined to doubt this statement he need only pick up the morning newspaper of any city of any size and be convinced that this is true. Hundreds of crimes of all descriptions are committed daily and statistics show that more than fifty per cent of persons committing crimes go unmolested and unpunished. Besides, there are the thousands of employees on our various transportation systems, in banks, stores, and in mercantile establishments, who are daily committing thefts of various kinds from their employers and whose nefarious operations are rarely uncovered, when one considers the actual number of thefts committed. – Summary by From the Preface