A robot,designed by Leonardo but recreated by Piero as a fire-breathing demon,is on the loose in Florence until Piero,who has orchestrated its retreat, is declared a hero and asked to take over power from the duke. At last Leonardo appreciates that this is the culmination of Piero's theft of his note-book as a means to rule Florence. Accordingly he makes sure that during the 'demon's' next outing Piero is discredited and the duke reinstated. This however alienates him from dim Lorenzo,who cannot see his father's villainy.