When Commissario Marco Leone of Rome's police discovers the murdered corpse of a Vatican scholar floating in the Tiber, he postpones a sabbatical trip abroad to investigate. The murder is only the first in a puzzling series of costumed and ritual assassinations. The mystery intensifies with attacks on specific chruches in the Eternal City....all built ovver the ruined chapels of an ancient god, Mithras. The investigative twists lead Leone to two American archaeologists excavating the Villa of the Papyri. They have uncovered two scrolls that, if authentic, could rewrite the history of early Christianity. With their help he discovers that Lucio Piso, a charismatic tycoon sexually abused by a current cardinal and bewtiched by the underground cult of Mithras. is the vengeful mastermind trying to take over the Italian government in a coup and take down the Catholic Church. Earthquakes shake St. Peter's Basilica. An explosion puts the pope in a coma. Church and government are in crisis.