The Police Agent (1867) is a milestone in the development of crime fiction. Its eponymous hero, the cunning Mr. Porion, a.k.a. Pere Cinnamon, does not employ his detective skills to pursue a vampire-like serial killer intent on bleeding children, but rather to protect him, while simultaneously serving other predatory aristocratic interests, such as providing the lecherous King Louis XV with a steady supply of virgins.

This crime novel Ponson du Terrail wrote may seem eccentric to 21st century eyes because the genre has undergone many refinements, but it remains fascinating as an example of its evolution. The Police Agent contains examples of deductive detection applied to a criminal investigation, as well as foreshadowing what became the "police procedural."

The Police Agent boldly asks: if the police and the criminals are on the same side, possessed of all the power and legal authority, who can play a heroic role, and how can he possibly prevail, escaping torture, murder and annihilation?