Editing Foucault's Pendulum (section)

== Plot summary ==
[[File:Pendule de Foucault au musee des arts et metiers.jpg|200px|thumb|left|The eponymous [[Foucault pendulum]] at the [[Musée des Arts et Métiers]] in Paris.]]
The book opens with a man named Casaubon{{Efn|Casaubon's name refers to classical scholar [[Isaac Casaubon]] and also evokes a scholar character in [[George Eliot]]'s ''[[Middlemarch]]''.}} hiding in the [[Musée des Arts et Métiers]] after closing. He believes that a secret society has kidnapped his friend Jacopo Belbo and is now after him, and that they will soon convene in the museum. As he waits, Casaubon [[flashback (literary technique)|reflects on his life]], but it is implied that he is an [[unreliable narrator]] whose mind has been warped by conspiracy theories.

In the 1970s in [[Milan]], Casaubon, who as a student had participated in the [[1968 movement in Italy|1968 Italian uprisings]], is studying the [[Knights Templar]] when he meets Belbo and his colleague Diotallevi. The former works as an editor in a publishing house and invites Casaubon to review a manuscript about the Templars. The manuscript, by Colonel Ardenti, claims he discovered a secret plan of the Templars to take over the world. Ardenti mysteriously vanishes after meeting with Belbo and Casaubon; Casaubon then moves to Brazil to pursue a relationship with a woman named Amparo and meets Agliè, an elderly man who implies he is the mystical [[Count of St. Germain|Comte de Saint-Germain]]. Casaubon's relationship with Amparo falls apart after attending an [[Umbanda]] rite, and he returns to Milan, where he is hired by Belbo's employer, Mr.&nbsp;Garamond,{{Efn|The novel's character "Mr.&nbsp;Garamond" is a reference to French publisher [[Claude Garamond]].}} as a researcher. Casaubon learns that in addition to a respected publishing house, Garamond also owns Manutius, a [[vanity press|vanity publisher]] that charges incompetent authors large sums to print their work.{{Efn|The name of the fictional publishing house (''Manuzio'') is rendered ''Manutius'' in the English translation; it is a reference to the 15th&nbsp;century printer [[Aldus Manutius]].}} Garamond has the idea to begin two lines of occult books, one for serious publishing and the other to be published by Manutius to attract more vanity authors. Agliè, now also in Milan, becomes a consultant to Garamond. Belbo grows jealous of Agliè's ability to charm Belbo's former mistress Lorenza.

Belbo, Diotallevi, and Casaubon become submerged in occult manuscripts that draw flimsy connections between historical events, and soon have the idea to develop their own as a game. Using Belbo's personal computer "[[Abraham Abulafia|Abulafia]]" and Ardenti's manuscript as a foundation, the three create what they call "The Plan" using a program that rearranges text at random. The Plan eventually becomes an intricate web of conspiracy theories about the Templars and their goal to reshape the world using "[[telluric current]]s", which are focused at the [[Foucault pendulum]]. In addition to numerous other historical organizations apparently involved in The Plan, the three invent a fictional secret society, the Tres (''Templi Resurgentes Equites Synarchici'', [[Latin]] for "the Risen again Synarchic Knights of the Temple").

As time passes, the three become increasingly obsessed with The Plan and wonder if it could be true. Diotallevi is diagnosed with cancer and attributes it to divine retribution for his role in The Plan. Belbo, overcome by jealousy over Lorenza, discusses The Plan with Agliè and claims to be in possession of a Templar map of the telluric currents; Agliè demands to see it and is refused. Agliè, Garamond, Ardenti, and many of the manuscript authors convince themselves they are the Tres, and that Agliè is their leader; the latter then forces Belbo to accompany him to Paris. Casaubon visits Belbo's apartment and reads his personal files, then goes to Paris and Foucault's Pendulum to see Agliè and his associates.

In the present, a group led by Agliè gathers around the pendulum for an arcane ritual. Casaubon sees several [[Ectoplasm (paranormal)|ectoplasmic]] forms appear, one of which claims to be the real Comte de Saint-Germain and denounces Agliè in front of his followers. Belbo is questioned but refuses to reveal what he knows, inciting a riot during which he is hanged from Foucault's Pendulum. Casaubon escapes the museum and flees to the countryside villa where Belbo grew up, soon learning that Diotallevi succumbed to his cancer at midnight on St.&nbsp;John's Eve, coincidentally the same time Belbo died.

Casaubon [[meditating|meditates]] on events and resigns to being captured by the Tres, where he plans to follow Belbo's lead and tell them nothing. While waiting in the villa, Casaubon finds an old manuscript by Belbo that relates a mystical experience he had when he was twelve, in which he perceived ultimate meaning beyond signs and semiotics. He realizes that much of Belbo's behavior, and possibly his creation of the Plan and even his death, was inspired by Belbo's desire to recapture that lost meaning.<ref>{{cite book |author=Bondanella |url=https://books.google.com/books?id=nfmdDpZNm30C&dq=Belbo+trumpet&pg=PA150 |title=Umberto Eco and the Open Text |page=150}}</ref>{{full citation|date=November 2022}}{{Efn|The mystical experience involved playing the trumpet. In 2008, Eco told an interviewer that he plays the trumpet every day, to recapture the feelings of his lost childhood.<ref>{{cite magazine |author=Zanganeh, Lila Azam |date=Summer 2008 |title=Umberto Eco, the art of fiction no.&nbsp;197 |url=http://www.theparisreview.org/viewinterview.php/prmMID/5856 |magazine=[[The Paris Review]] |issue=185}}</ref><ref>{{cite book |author=Rorty, R. |author-link=Richard Rorty |title=The Pragmatist's Progress |date=July 2000 |publisher=Rowman & Littlefield |isbn=978-084769061-9 |edition=annotated |page=90}}</ref>}}