When Antonio Ferrara of the Italian Polizia di Stato discovers that the seemingly random victims of a Tuscan serial killer are all illegitimate descendants of one Giovanni de Medici, a 15th century Florentine banker, his superior scoffs at his theory while the Italian military police caution him to leave the case alone on the basis of "national security." Undeterred, Antonio enlists Medici scholar Rachel Fuller and, together, they travel to America to unlock the secret.