Pope Alexander sends Cesare to Catherina Sforza’s castle at Forli to demand that she swear allegiance to Rome while he himself travels to Florence in disguise to hear the increasingly powerful Savonarola preach – not knowing that Della Rovere is there too, getting Savonarola’s blessing on his plot to assassinate the Pope.
At Forli, Catherina receives Cesare graciously and proceeds to seduce him, but subsequently refuses to swear allegiance to the Pope. Enraged, Cesare kills her cousin Giovanni – as revenge for his brutal treatment and rape of Lucrezia during their ill-fated marriage.
In Rome, Lucrezia, Vanozza and Giulia put their plan for reform into action by funding the renovation of a run-down brothel. Lightning strikes St. Peter’s Basilica during a Mass and the roof collapses – Alexander is almost killed, but courageously tries to save the lives of choirboys trapped in the rubble.