Angels & Demons follows Harvard symbologist Robert Langdon, as he tries to stop what seems to be the
Illuminati, a legendary secret society, from destroying the Vatican
City with the newly-discovered power of
antimatter.
CERN director Maximilian Kohler discovers one of the facility''s most respected physicists, Leonardo Vetra, murdered in his own secured, private quarters at the facility. His chest is branded with a symbol — the word "Illuminati", formed as an ambigram, using a burning hot object. Instead of calling the police, Kohler researches the topic on the Internet and finally gains contact with Professor Langdon, an expert on the Illuminati. Kohler requests his assistance in uncovering the murderer.
What Langdon finds at the murder
scene frightens him: the symbol appears to be authentic, and the legendary secret society, long thought to be defunct, seems to have resurfaced. Kohler calls Vetra''s adopted daughter Vittoria to the scene and it is later revealed that the Illuminati has also stolen a
canister containing a quarter of a gramme of antimatter — an extremely deadly weapon that could destroy an entire area when in contact with matter. When charged with electricity at CERN, the canister''s magnetic field controls the drop of antimatter to float in pure vacuum, ensuring safety; but when it is taken away from its electricity supply, the canister will automatically switch to using its back-up battery, which lasts for only 24 hours. The horrible truth is that now the Illuminati has put the stolen canister somewhere in Vatican City, with a security camera in front of it as its digital clock counts down to the explosion.
It turns out that the papal conclave is being held that night, making it the perfect time for the Illuminati to hide the antimatter inside the Vatican and destroy all the important people in the Roman Catholic Church. Cardinal Mortati, host of the election, discovers that the four preferiti,cardinals who are the top picks in the current Pope election, are missing. Actually, they have been kidnapped by the Hassassin in the book, who is also the killer of Leonardo Vetra. Langdon and Vittoria therefore set off to the Vatican in hopes to find the killer and retrieve the antimatter, but Kohler succumbs to illness and cannot go with them. St. Peter''s Basilica in Vatican City.
After they arrive, their search is assisted by Camerlengo Carlo Ventresca and the Vatican Swiss Guards, including Commander Olivetti, Captain Rocher and Lieutenant Chartrand. Clues found in the Vatican Archives take Langdon and Vittoria through many tourist attractions in Rome following the so-called "path of illumination", as they seek out locations which the book calls the "Altars of Science". Each altar relates to one of the classical elements (Earth, Air, Fire and Water) which were once considered to be the only constituents of all matter.