With intrigue, complexity, and adventures, Foucault's Pendulum is easily one of Umberto Eco's most engaging novels. The plot revolves around the protagonist, Casaubon, who becomes fascinated by the Order of the Knights of the Temple, the Templars. Seemingly mandated by fate, Casaubon continually finds himself pulled back to an investigation of the remnants of the order, especially after the colonel's disappearance. Other pursuits, like family and wealth, fall to the wayside repeatedly because Casaubon compulsively pursues the investigation. Eventually he loses control and succumbs to the violent demands of his rivals.
In college at the University of Milan, Casaubon writes his senior thesis upon the Templars. He makes friends with colleagues at the local paper, Belbo and Diotallevi. After a retired colonel appears with a secret map and plans by the Templars to return and enact their revenge for past suppression, the three friends are hooked. The colonel disappears, but Casaubon gives the entire affair a back seat pass as he pursues his romance with Amparo in Brazil. Returning to Milan, he gets a job working for Belbo at his own paper. Always interested in the occult, Casaubon finds himself continually in trouble for not providing proper scientific evidence for his work, so a Mr. Allier, a scientist from Brazil, is brought in as a consultant. Allier reintroduces the friends to their Templar Order mystery.
Various roadblocks separate the crew from the discovery of the Templar conspiracy. Casaubon gets his girlfriend Leah pregnant, and they have a baby together, in addition to his relationship to Amparo. Allier's connection to Brazil -- and Amparo -- is not accidental, by the way. Diotallevi is diagnosed with cancer, remains in the hospital for the latter half of the book, and eventually dies. For his part, Belbo confides the information about the secret plan to Allier, who later takes him to Foucault's pendulum, along with Allier's diverse companions, and tortures him for secrets. Eventually Belbo dies at the pendulum from wounds sustained in the questioning. In the end only Casaubon survives, but he lives a tortured, paranoid existence afterward, convinced that Allier and his crew will murder him to prevent witnesses of their pursuit of the Templar treasure.
