"Brilliant Deduction" asks the question "who are the greatest detectives ever" and then attempts to find an answer which doesn't involve fictional characters. The result is nine men whose careers in the 19th and early 20th century represent the heroic years of real-world detection, from the very first full-time professionals to the Prohibition era. Each chapter examines a different detective (or, in one case, a detective partnership) who became a legend in his own time, and in some cases a full-fledged celebrity. At the same time, the larger narrative ties these individual histories together to explore how real-life detectives rose to such fame for nearly 100 years, then fell back into obscurity.