Foucault's Pendulum

In this adventure novel, three editors in Milan cook up a hoax that connects the medieval Knights Templar with other occult groups from ancient to modern times. They produce a map indicating the geographical point from which all the powers of the earth can be controlled—a point located in Paris, France, at Foucault’s Pendulum. But the joke becomes all too real when other occult organizations—including Satanists—get wind of the Plan, and they go so far as to kill one of the editors in their quest to gain control of the earth.