Paris: July 1890. Inspector Achille Lefebvre and his wife Adele are enjoying their stay at a seaside resort–until a body found hanging from a bridge in a public park demands the Inspector’s attention.

Is it suicide or murder? A twisted trail of evidence draws Inspector Lefebvre into a shadowy underworld of international intrigue, espionage, and terrorism. Time is of the essence; pressure mounts on the Surete to get results. Achille’s chief orders him to work with his former partner, Inspector Rousseau, now in charge of a special unit in the newly formed political brigade. But can Achille trust the detective who let him down in another case?

Inspector Lefebvre uses innovative forensics and a network of police spies to uncover a secret alliance, a scheme involving the sale of a cutting-edge high explosive and an assassination plot that threatens to ignite a world war.

Amid the hustle and bustle of the Paris 1889 Universal Exposition, workers discover the mutilated corpse of a popular model and Moulin Rouge Can-Can dancer in a Montmartre sewer. Hysterical rumors swirl that Jack the Ripper has crossed the Channel, and Inspector Achille Lefebvre enters the Parisian underworld to track down the brutal killer. His suspects are the artist Toulouse-Lautrec, an acrobat at the Circus Fernando named Jojo, and Sir Henry Collingwood, a mysterious English gynecologist and amateur artist.

Pioneering the as-yet-untried system of fingerprint detection and using cutting edge forensics, including crime-scene photography, anthropometry, pathology, and laboratory analysis, Achille attempts to separate the innocent from the guilty. But he must work quickly before the “Paris Ripper” strikes again.

At the public execution of the anarchist assassin Laurent Moreau, the outgoing Chief Inspector warns his protege, the newly promoted Lefebvre: “I’ve heard that some of Moreau’s cronies have sworn revenge. You don’t want to get killed your first week as chief.”

Meanwhile, Lefebvre is charged with investigating the disappearance of the Baron de Livet, a brash millionaire with connections to Russian spies and a history of gambling, womanizing, and fighting in duels. The case is more complicated than it seems, of course, and Lefebvre and his team must make sense of a poisoned maid, an unidentifiable stagecoach, and a missing briefcase full of cash. The Baron’s connection to the world of international espionage means that, if the Inspector isn’t fast enough, the Baron’s disappearance might trigger a war.

And Lefebvre mustn’t forget those stalking anarchists who are out for his blood, as he searches for the man who wasn’t there…