Caleb Levi, former college basketball star turned history professor, is back for his sixth summer of research in Florence, Italy. While there he translates the reports of Niccolo Nannrone, a 15th century spy who served a politically ambitious cardinal, and learns of nefarious plots and brutal murders in the late 1400s. Then one day, to his great surprise, Caleb witnesses a death in the 21st century that mimics one he had just read about in Nannarone's latest report. Against his better instincts, Caleb looks into a possible connection between those two deaths some 500 years apart. He has barely started, however, when an assailant emerges from the darkness and attempts to kill him. This draws Caleb's fellow scholars to join him in a full-scale investigation. They soon are deep into the intrigues of 15th century Florence and unexpectedly a mystery from the World War II era in that city, all the time pursued by an array of assassins. But what started as a probe into the possible murders of two women eventually leads Caleb to a monstrous conspiracy--and a final life or death confrontation on the massive roof of Florence's magnificent cathedral, Il Duomo.