The Saville Communion By Arturo Perez Reverte

Another splendid novel by this acclaimed Spanish author. The setting is Seville where controversy over the demolition of a four hundred year old church enjoins greedy bankers, a comical trio of villains, a self serving Arch Bishop and an old priest and his supporters in a deadly battle of devious plots and counter plots. The outcome of the battle hinges on a very old provision in the churches grant that states that as long as mass is said each Thursday morning at 8:AM, ownership will never revert to the city.
A computer "hacker" that Rome chooses to identify as "Vesper" has entered the Pope’s personal computer with a message that he should intervene and protect the tiny crumbling old church.

Because of the intrusion, a special investigative branch (problem solvers)of the Vatican sends their most experienced man to "find out what is going on and report". There are civil and church politics involved and there have been two deaths connected with the church which makes the problem even more delicate. The priest, Lorenzo Quart, goes to Seville and becomes intrigued and involved with the old priest who always manages to hold mass on Thursdays; he conducts his mass in Latin conducts himself in ways that irritate the Arch Bishop. He also meets the old priests’ young assistant, and an unorthodox American girl who is an archaeologist who is trying to restore the old pile but is also a nun. He meets other people who support the old priest's efforts; among them, a beautiful woman recently separated from the man who has the most to gain from the demolition and return of the title to the land to the city. Through her and her aristocratic mother, Quart learns more about the history of the church and Seville than he bargained for. He, also becomes emotionally involved with the young woman. The Arch Bishop turns out to be an old enemy of Quart and not only fails to assist him but attempts do him harm.
There is intrigue, blackmail, another dead body, this time a murder, marvelous characters and dialogue, most interesting religious philosophy and considerable insight into church politics. The identity of "Vesper" is rather a surprise