A Novel

By Fred Vargas

Translated from the French by David Bellos

Simon & Schuster. 353 pp. Paperback, $14

A town crier in modern-day Paris? That's both the conceit and the launching pad of Fred Vargas's Have Mercy on Us All, which manages to be both an ingenious thriller and a meditation on code, communication and miscommunication.

The crier is Joss Le Guern, a fiftyish former sailor descended from a line of medieval town criers, who takes up the family business as a last-ditch career move in a particularly hard-luck life. After wrecking his trawler, Le Guern endures years of unemployment and menial labor until a genial ancestor appears to him in a vision and advises resurrecting the family business: "News is the one line of goods that never runs short on this planet, it's the one tipple people never get too much of," his great-great-grandfather tells him. "When you're a crier, it's like you're giving the breast to the whole of humanity. You never run out of milk or of suckling babes."

Naturally, Le Guern is skeptical, but he succeeds handsomely: There's no shortage of Parisians willing to put their thoughts to paper and tuck them into Le Guern's lockbox with five francs for the pleasure of hearing their words in a public park. Voila -- your spare sofa for sale, your philosophy of the world or your complaint about the neighbor's dog is part of the evening news.

This confluence of medievalism and modernism (Vargas is a Parisian archaeologist specializing in the Middle Ages) informs every page of Have Mercy on Us All in the same way that Caleb Carr examined modern America through the prism of early 1900s Manhattan in The Alienist. Vargas sneaks in her parallelisms in delightful and clever ways, starting with the very contemporary premise of this thriller: Someone is trying to spread the Black Plague in modern Paris and has chosen the medieval method of using a town crier to spread the news.

At first, the messages are cryptic -- bits of nonsense inserted between Le Guern's usual recitation of rants, recipes and marriage proposals -- but before long they become tied in with an odd graffito that's popping up in Parisian apartment buildings: a reversed 4, painted on every door except one. The residents of those unmarked apartments begin turning up dead, with rat-flea bites and blackened flesh. But the cause of death in each case is strangulation, not pox, and the blackening of their skin is nothing but charcoal.

That surprise is only one of Vargas's creepy twists, and she turns another when it becomes clear that the story isn't Le Guern's or even the unknown assassin's. Enter Commissaire Jean-Baptiste Adamsberg, a street cop recently promoted to the Brigade Criminelle, the Parisian murder squad. Methodical and intuitive, world-weary and skeptical, the middle-aged Adamsberg is a Gallic cousin to Ruth Rendell's Chief Inspector Wexford, and Have Mercy on Us All is as much about the complicated commissioner as it is about the plague. As his assistant tells Adamsberg's sometime lover Camille, "The day when God made Adamsberg, He'd not slept at all well the night before."

Adamsberg deduces, correctly, that the goal isn't a widespread pandemic of disease but of fear. As panic and rumor begin to spread and Parisians start painting inverse 4s on their own doors to stem the imaginary contagion, Adamsberg's task becomes twofold: to detect the method behind a serial killer's madness and to put a halt to an outbreak of mass hysteria.

Vargas's point, of course, is that 15th-century Europe and the 21st-century world aren't that different at their cores, and her hypothesis is summed up neatly in the person of Le Guern, whose role in the public square isn't much different from that of any blogger or cable-news talking head. As one character observes of the old fisherman, "Joss probably couldn't tell men from mullet anymore, seeing the way he treated both kinds of catch, that is to say, making his money by pulling out their guts."

It's not too far from Le Guern's philosophy to modern-day cable news, where incisiveness and accuracy will always take a back seat to sensationalism and celebrities. As Vargas implies, plagues go by different names these days -- SARS, anthrax, avian flu -- and CNN and Fox News have become the town squares, with Anderson Cooper and Shepard Smith our evening criers. *

Kevin Allman is the author of the novels "Tight Shot" and "Hot Shot."