Nicolas investigates the mysterious death of Viscount Lionel de Ruissec. Was it suicide or murder? Nicolas discovers that the murder is linked to a plot against King Louis XV and reigning favorite Madame de Pompadour.

Commissioner Lardin has apparently been murdered, and letters comprising the King have also been stolen. Who could have wanted him out of the way? Will Dr. Scemacgus, Nicolas' good friend, have to be brought in for questioning?

Having just risen to the rank of police commissioner at the famous Chatelet in Paris, Nicolas Le Floch, a handsome young man from Brittany, is put in charge of investigating the murder of the young Viscount Lionel de Ruissec. But the viscount's family is thwarting the investigation, and doesn't want an autopsy. Le Floch discovers that the young man died after being forced to eat molten lead.

With the highly efficient help of Inspector Bourdeau, his second-in-command, and wise advice from Mr. de Noblecourt, a retired judge, Nicolas Le Floch uncovers a dark conspiracy. Caught up in a serious corruption scandal, the Count de Ruissec had recently had Army Lieutenant of Dragons Jean de Langremont killed, to silence him.

With the highly efficient help of Inspector Bourdeau, his second-in-command, and wise advice from Mr. de Noblecourt, a retired judge, Nicolas Le Floch uncovers a dark conspiracy. Caught up in a serious corruption scandal, the Count de Ruissec had recently had Army Lieutenant of Dragons Jean de Langremont killed, to silence him.

Beautiful Elodie Galaine is discovered strangled to death at a party thrown in Paris by Louis XV. Nicolas le Floch leads the investigation into the strange doings of the Galaine family.