The Confessor (Gabriel Allon, #3) (2003) by Daniel Silva
Israeli Mossad Agent Gabriel Allon is in Venice restoring a 16th century altarpiece by Bellini located in the San Zaccaria church. Allon, using his undercover name of Mario Delvecchio and speaking only Italian, learns about the murder of his old friend, Professor Benjamin Stern, who had been working secretly on a book about the Catholic Church during World War II.
Gabriel’s search for the assassin takes him throughout Europe and the Vatican. Even the Pope is a character in this spy thriller.
Silva knows how to keep his readers on the edges of their seats, turning pages late into the night. Very good reading with great characters.