Told in the form of a kind of intellectual game, three friends compile a fictitious Plan which stretches throughout history and hopes to combine all conspiracy theories, also embracing unlikely opposites. The novel is an encylopedic work, moving critic and novelist Anthony Burgess to comment that it needed an index. Published in 1988, translated into English by William Weaver.
The following conspiracies and secret societies appear in Foucault's Pendulum:
The main plot of "The Plan" involves the Knight Templars having discovered a secret energy source during the crusades, probably related to Ark of the Covenant or the Holy Grail (or both), which makes it possible to control energy flows (resembling Qi) relating to the movement of Plate tectonics. One instrument involved in controlling the energy flows is (the scientific instrument) Foucault's pendulum.
The discovery is hidden away purposedly and the Knights Templar trigger their own destruction, while at the same time hiding independent cells in several corners of Europe. These cells are set up to meet each other at distinct long-term intervals and in the end reunite and recover the hidden energy source to achieve world domination when the time is right.
However, the adaptation of the Gregorian calendar disrupts the time table and the groups lose track of each other, creating several secret societies searching for each other throughout history.