Foucault's Pendulum By Umberto Eco

One Colonel Ardenti, who has unnaturally black, brilliantined hair, a carefully-groomed mustache, wears maroon socks, and who once served in the Foreign Legion, starts it all. He tells three Milan book editors that he has discovered a coded message about a Templar Plan, centuries old and involving Stonehenge -- a plan to tap a mystic source of power far greater than atomic energy.The editors, who have spent altogether too much time rewriting crackpot manuscripts on the occult by fanatics and dilettantes, decide to have a little fun. They'll create a Plan of their own. But how?Randomly they throw together manuscript pages on hermetic thought; The Masters of the World, who live beneath the earth, The Comte de Sain-Germain, who lives forever. They add Satanic initiation rites of the Knights of the Temple, Assassins, Rosicrucians, Brazilian voodoo, the Third Reich. And they feed all this, and much more, into their powerful computer, Abulafia.A terrific joke, they think, until the Plan assumes and life and power of its own, and turns deadly -- as people mysteriously begin to disappear, one by one, starting with Colonel Ardenti.