We begin with one-legged Vito Piranese, and his assignment is to find out about the movements of Franck Chopin, an entomologist specialising in flies who occasionally is given spying projects by Colonel Seck through Maryland, the boss nicknamed after the kind of Gauloise he smokes. Piranese (there are many references to authors, films, songs, etc) is given the code 13, 47, 14: this is an indication that at 13:00 he takes a 47 bus at the Gare du Nord and at the fourteenth stop makes an exchange of papers with another agent, and he remembers the numbers because his birthdate is '47, everyone can remember 13 and 14 comes after it. It's all very ludicrous, as it's of course meant to be.
Lac's world is one in which acute observations are made, in which inanimate objects are given human attributes, flies are imagined to possess human sensibilities, and many actions of a human (as opposed to an animal) are slightly obsessively dissected, such as Chopin eating a banana. It is a world in which great detail is all-important, trade names and numbers are strewn about, digressions being many.
Chopin 'situates and dates' aspects of his body ('from the gash on his knee (Baccarat, 1957) to the stiffness of a metacarpus (Canton, 1980)'; when kidnapped and stowed in the boot of a car he mentally notes 'ropes and greasy rags, jack, spider brace and 10W50 can of oil'; and there are even a few fictional references to articles he's written: '1. CHOPIN (F.), « Les conditions expérimentales de la performance en autonomie du vol chez la psychode (Psychoda alternate) », Annales de parasitologie, XX, no 6, 1972, pp. 467-473.'
Some of the ludicrous is based on factual truth: where Chopin must meet Seck on one occasion, in the grounds of Thiais cemetery, seems accurate down to the last detail (I've spent several hours tracking down graves in the obscure place), although I was unaware of the (very real) existence of Zog I of Albania's memorial.
And some is so very ludicrous (though highly ingenious) as to be pure invention (I think): the planting of nano-microphones on the bodies of flies delivered to subjects in 'presents' of bouquets of flowers so the flies can 'spy' on them and Chopin records their eavesdropping remotely. There is even (or of course?) some fly empathy, and we learn of the most dreaded enemy of the fly since 1631 (which Wikipédia (and not Echenoz) tells me marked the foundation of La Gazette by Théophraste Renaudot): the year of France's first newspaper.
I've just mentioned a few things, not Chopin's relationship with women (particularly with Suzy Clair), even Vital Veber, the main subject of the surveillance, or any of the other characters. Echenoz packs a great deal into 189 pages, and they have to be savoured by re-reading.
And I don't remember anyone going to the Canal Saint-Martin in the novel, but it's a nice touch having the telephoto shot of Echenoz himself on one of its bridges.