Cosimo Medici replaces his late father in Florence's Signoria, after 20 years of grooming. He must decide if he will declare war.
As the war with Milan puts a heavy burden on Florence, Cosimo pushes morale and economy by doing the impossible: building the cathedral dome.
Albizzi takes advantage of the plague to turn the people against Cosimo, two Medici family members are missing and Marco reveals a shocking confession.
Cosimo's wife tries to get help from a member of Signoria, after he got arrested. Piero tries to refute the charges, while Lorenzo takes a more extreme way.
During his exile in Venice, Cosimo becomes attracted to a slave woman. Contessina meets her childhood sweetheart in Florence.
Cosimo returns to Florence while Rhinaldo is summoned to court for treason and tyranny. Rhinaldo confesses that he murdered Giovanni before his exile.
Cosimo faces pressures and doubts before the imminent election of a new member of the Signoria to take the post of Rhinaldo.
Pazzi succeeds in persuading the Pope to sack Cosimo, but Cosimo is unwilling to surrender.