Florence in the year 1518 is riven by scientific and sociological change caused b the wonderful devices of the Great Engineer, Leonardo da Vinci. Now he is old and lives as a recluse working behind the walls of his castle. The Raphaelites, artists and anti-technologists led by Raphael of Urbino, call for his excommunication. Pasquale di Cione fiesole, an apprentice painter witnesses an assassination attempt on Raphael at a Cathedral service. The weapon falls into his hands, and he is soon on the run from engineers and artists, desperate to prove his innocence.