Bright Summaries - Have Mercy on Us All by Fred Vargas (Book Analysis): Detailed Summary, Analysis and Reading Guide

Joss Le Guern is a former Breton sailor. After he is shipwrecked, he attacks the owner of his ship and almost kills him, which leads to him being sent to prison for two years. After he gets out, he moves to Paris. This is where his great-great-grandfather appears to him during a heavy night of drinking and suggests that he take up the family job as town crier. Town criers used to deliver the news and announcements made by the inhabitants of remote villages.

Joss therefore decides to do just that and sets up a box in Paris where the inhabitants can put announcements and notes about how they are feeling. He cries out the news three times a day on a square somewhere in Paris. However, for the past three weeks he has been receiving strange messages written in Old French and Latin which announce the return of a terrible plague. He decides to go to see an old friend, Decambrais, a former prisoner nicknamed the scholar who identifies the messages as extracts from manuscripts describing different plague epidemics. The two decide to warn the police and go to see Adamsberg.

During this time, the Commissaire Jean-Baptiste Adamsberg has been transferred to the Paris murder squad. A young mother has come to lodge a complaint about the strange inscriptions on the doors of her building: an upside-down 4 written in black ink. After consulting a medievalist, the commissaire discovers that the number is actually a cross written in one stroke and is supposed to ward the plague away from the houses it is written on. These curious symbols begin to appear in flats across Paris. Adamsberg establishes a link between Josss mysterious messages and the symbols which are spreading across the city. His curiosity leads him to go to listen to Josss announcements to get a better idea of what these strange messages might mean.

Joss leaves his squalid one-bedroom flat to live with Decambrais, where he meets the other tenants: Damascus, who has a skate shop; Lizbeth, a former prostitute from America and something of a diva; Eva, who has just run away from her violent husband; and Marie-Belle, Damascuss unassuming sister.

The narrator takes the reader to a see a woman called Narnie, whose son-in-law Arnaud is visiting her. He is apparently the one who is tracing the signs on the doors. The old woman is raising rats, which she believes are carrying the plague, and is sending Arnaud with letters filled with fleas to future victims. She is convinced that her family has magic powers, since her parents survived a plague epidemic.

Josss messages for the day announce the first victims of the plague. A body is discovered in a block of flats in Paris and an envelope full of fleas is found near the body. The paper is identical to the kind used for the missives that the town crier has been receiving. Adamsberg and his assistant Danglard launch an investigation. They learn that the victim did not die of the plague, but was bitten by fleas and then strangled. Two other victims are found shortly afterwards. The people of Paris begin to panic: they trace the number four on their doors to protect themselves from the plague. Adamsberg is convinced that the killer is among the crowd that comes to hear Josss news every morning.

The press gets wind of the rumour and reminds the residents of Paris about the plague epidemic which hit the city in 1920. Adamsberg asks a psychiatrist for help in order to draw up the killers psychological profile. He thinks that culprit is personally linked to the plague. The commissaire does some research on the 1920 epidemic. He is also intrigued by Marie-Belles other brother, who she takes care of because he seems to be psychologically fragile.

A new victim is discovered in Marseille and Adamsberg goes to investigate. As he continues his investigation, he discovers that the rich are now wearing diamonds on their left ring finger to protect themselves from the epidemic. The commissaire remembers that he saw a flash from someones hand during Josss crying. When he gets back to Paris, he takes Damascus in for questioning and sees that the man is indeed wearing a diamond on his left hand. He therefore becomes the main suspect. Moreover, he has fleas on him and has direct access to Josss box. Adamsberg also discovers that he does not have a clean criminal record: he was wrongly accused of having thrown his girlfriend out of a window.

A stranger then comes to the police station claiming that his life is in danger: he has found a flea-filled envelope under his door. Adamsberg guesses that he has a mysterious past. Under pressure, the young man eventually admits that he was part of a band of seven gangsters who tortured a man and raped his girlfriend.

Adamsberg establishes a link with the past of Damascus, who had perfected a device for manufacturing honeycomb steel alloys which made them far less likely to fail. A major company boss then kidnapped him to steal his patent. After she was raped, his girlfriend committed suicide and Damascus was accused of murder. With the help of his grandmother, he prepared his revenge in prison using the family myth about the plague. His aim was to eliminate the gangsters who had attacked him and his girlfriend. Narnie is arrested and admits to everything, as she is convinced that the victims truly did die of the plague. Her family survived a plague epidemic in Clichy in 1920. There are still three of Damascuss torturers to be killed.