Foucault's Pendulum

Foucault's Pendulum is a 1988 novel by Umberto Eco, and a notable work of conspiracy literature.

While The Da Vinci Code plays the conspiracy theory view of history completely straight, and Illuminatus! subverts it wildly, this novel is an elaborate and sometimes savage Deconstruction.

The main characters are:

 * Casaubon: Protagonist and narrator. Also an intellectual dilettante and expert on The Knights Templar.
 * Belbo: Editor who is haunted by failure and frustrated desires.
 * Diotallevi: Belbo's partner who is obsessed with all things Jewish and Cabbalistic.

The narrative contains numerous flashbacks, dream sequences, and historical anecdotes, but the basic plot is this: Casaubon, while working on his degree, meets Belbo at a bar one night and they have a conversation during which Casaubon reveals his expertise. Belbo, who works for a publisher named Garamond who specializes in academic works and doubles as a vanity press, finds Casaubon interesting and invites him to visit the publisher. Casaubon is introduced to Diotallevi and is allowed to be present while they interview an author, Colonel Ardenti, who presents a manuscript. This turns out to be a book purporting to expose the secret of the Templars, which the author believes is dangerous to know.

Sure enough, the man disappears mysteriously, but the police investigation goes nowhere. Casaubon moves to Brazil, where he gets a radical socialist mixed-race Brazilian girlfriend named Amparo and later meets a man named Agliè who is an expert in occultism. Agliè likes to tell historical stories as though he were there in person. Eventually, Amparo leaves Casaubon, and he moves back to Italy.

Upon his return, Casaubon becomes a freelance researcher and accepts work from Garamond, first a history of metals, and then a history of occultism. He also meets and falls in love with a woman named Lia. During their projects, he, Belbo, and Diotallevi meet many odd characters from the occult word with the help of Agliè. Inspired by the theories they encounter, as well as Ardenti's, they decide one night to create their own history of the world based on the idea that an occult conspiracy is the cause of all historical events.

Over Lia's objections, Casaubon and his partners become more and more invested in the Plan they have created, but then unwisely start hinting to Agliè that they possess knowledge he does not. Agliè, Ardenti, and other members of the European occult community decide that they are the ones who are meant to be in control of history, and start chasing after the (completely falsified) secret of the Plan.

This book contains examples of the following tropes :

 * Ancient Conspiracy / Conspiracy Kitchen Sink : Played with Serial Escalation
 * Ambiguously Jewish: Diotallevi
 * Arc Number: 120.
 * Arson Murder and Jaywalking: A really peculiar inversion with the garrulous publisher's habit of starting out hyperbolic in his praise of things and then (apparently without realizing it) taking an abrupt downturn. E.g. "It is a palace! A dwelling fit for kings! I'll put it even more strongly: It's a genuine Piemontese villa!"
 * An example done straight is in when Casaubon mentiones the Borborites, who rip out fetuses from women's bodies, crush them in mortars and eat them with honey and pepper. Diotellavi says: "How revolting, honey and pepper!"
 * Author Avatar: A lot of Belbo's stories about his wartime childhood are directly taken from Eco's biography. Especially the trumpet episode.
 * Big Bad: Agliè.
 * Bilingual Bonus
 * Conspiracy Theorist : Subverted hard. The three protagonists all start out as Genre Savvy Deadpan Snarkers lampooning Conspiracy Kitchen Sink theories in general... but as the the book nears its end, they become raving Conspiracy Theorists themselves, seeing symbolism and dark secrets behind absolutely everything.
 * Deconstructive Parody : The whole book does this to the Conspiracy Literature genre. Lampshaded numerous times.
 * Epigraph : Opens each chapter...
 * Fake Real Turn: The Plan.
 * Fascist Italy: Belbo tells long stories from his childhood, which took place during Mussolini's rule.
 * Femme Fatale: Lorenza, with a few twists.
 * Genius Bonus / Shown Their Work : After all, it is an Umberto Eco novel...
 * Gone Horribly Wrong : Belbo, Casaubon and Diotallevi create "The Plan", an elaborate and ridiculously Trope Overdosed Conspiracy Theory as nothing more than a fun project for killing some free time and for mocking all the Conspiracy Kitchen Sink theories and secret histories they were forced to read while editing the manuscripts of various wacko authors for publishing. Their whole prank gradually starts getting out of hand and sounding far too real, since it's often even more convincing than all the pulp conspiracy theories it was supposed to make fun of in the first place.
 * How We Got Here: Casaubon's narration
 * Kabbalah: The branches/spheres of the kabbalistic tree of life serve as chapter headings.
 * Last Name Basis: The three main characters.
 * Ley Line: Part of the conspiracy theory.
 * No Name Given: The first names of Casaubon and Diotallevi are never revealed.
 * Casaubon's first name may be Pim. However, only Lia calls him that, so it might be just a nickname.
 * Numerological Motif: Lia gives Casaubon a talk about the real meanings. The number one is special because every human is, well, one human and has one head, heart, nose, mouth, private part etc.; two is special because two people make a couple, and humans generally have two hands, feet, eyes, ears etc.; three OTOH is so special because our bodies don't have three of anything (but man + woman + child make a family); etc.
 * Older Than They Look: Agliè. Maybe.
 * Readers Are Geniuses
 * Really Seven Hundred Years Old: Agliè. Or is he?
 * Redemption Equals Death
 * The Reveal: when we find out that the mysterious document that the Plan is based on
 * Shakespeare in Fiction: Or in Meta Fiction, at least - Belbo's writings about The Plan include an excessively convoluted theory about Shakespearean authorship.
 * Written in a narrative style with Belbo imagining himself as a reincarnation of the true original writer.
 * Shout Out: Hundreds if not thousands of them. Belbo's files are especially crammed: one reads like a crazy Troperiffic pastiche in which each paragraph (maybe each line) references a different nineteenth century adventure, mystery or conspiracy story. Did we say Genius Bonus?
 * The Password Is Always Swordfish: Played with. Casaubon tries to figure out the password to Belbo's computer, which asks: "Do you know the password?" Since Belbo is his close friend, he tries numerous expressions he thinks Belbo could've used, but none of them work. Eventually, he angrily types: "No." This is the password. (There's a deeper reason for this: In order to gain knowledge, you have to admit that you don't know a specific thing.)
 * There Are Two Kinds of People in The World: When Casaubon and Belbo meet for the first time, Belbo talks about how there are four kinds of people in the world: "cretins, fools, morons, and lunatics."
 * Unreliable Narrator: Casaubon, by the end, doubts his own sanity, and questions how much is true of what he had seen.
 * Victim Falls For Rapist: Subverted. When Amparo, as she told, noticed a guy approaching her in the night on the street, and suspected he wanted to rape her, she offered him to have sex. He ran away, because he wanted to hurt women, not sex.
 * Women Are Wiser: Lia.