Too busy chortling over their PC, Casaubon, Belbo, and Diotallevi don't consider that even an outrageous theory can tread on dangerous ground-until Belbo disappears and Casaubon begins a serious search for the Masters. The problem is to find occult links between, for example, the cabal and the spark plugs of a car.'' The result is a book uncovering the Plan, an underground movement operated by the Masters of the World.

Joined by Diotallevi, an authority on cabalistic word permutation, and with the help of a word processor, the team undertakes construction of a bogus study of the occult, a random sorting of hermetic writings: ''The challenge isn't to find occult links between Debussy and the Templars. Belbo's boss-a wizened operator of literary scams-wants to cash in on some New Age trade and suggests that Casaubon and Belbo throw together a history of the occult.

Casaubon meets up with Belbo, an underpaid scholarly editor amused at the heaps of New Age submissions crossing his desk-much of it, inevitably, touching upon a secret history of the Templars. Templar legends-in varying degrees of silliness-have been cropping up ever since: the movement went underground it was buried within the Rosicrucians it all connects with Atlantis, Stonehenge, the pyramids, etc. Casaubon has written a thesis on the medieval Templars-a martial order of monks founded initially to protect Crusaders en route to Jerusalem, and eventually disbanded by Pope Clement. From the Conservatoire des Arts et Metiens, the museum of technology in Paris, Casaubon narrates the tale of how a literary gag got out of hand, leading to violence, murder, mayhem. As he did in The Name of the Rose (1986), Eco begins here with a teasingly slow windup followed by a narrative that kicks into high gear about one-fifth of the way in. A first-rate, highbrow mystery packed with wit, satire, and erudition.

Foucault's Pendulum by Umberto Eco