Paris, 1899. President Félix Faure has just died in the arms of his mistress. While the Republic is on the verge of explosion, Prefect Lépine is called back to business. At the same time, at the prefecture, Inspector Jouin was mobilized on a large-scale investigation to identify "the unknown person in the suitcase".

The courtesan Meg, who became a spy on behalf of Puybaraud, head of the police and sworn enemy of the Prefect, infiltrates the Guérins. At the Surêté of Paris, Jouin investigates with Commissioner Cochefert the case of the bloody suitcase and the disappearance of Joséphine Berger. Fiersi is assigned to the investigation.

Inspector Jouin fells in love with Jeanne Chauvin, a young lawyer with a strong character, who could not practice but served as an assistant to Master Weidmann in the Jewish district of La Vilette. Jeanne decides to help him in the Berger case. For her part, Meg receives Madame Lépine, the prefect's wife, at home, whose penchant for artificial paradises has not escaped Commissioner Puybaraud.

Tension is mounting in the streets of Paris days before the opening of the Dreyfus trial while Lepine manages to resolve trap set for his wife to his own advantage. The Berger case continues.

As more evidence appears against Sabran in the investigation into Josephine's murder, Meg has fallen under his spell.

Jules Guerin takes refuge in Rue Chabrol. Fiersi distances himself from Puybaraud because he's sickened by the Berger case, giving Jouin an essential clue in his investigation.

Meg tries her last ploy with the Prefect while thinking about the future and Jouin tries to find out the whole truth about Sabran and in the process damaging his chances of keeping Jeanne.