Prince Of Foxes [1949]

In 1500, Duke Cesare Borgia hopes to marry his sister (widowed by poison) to the heir apparent of Ferrara, which impedes his conquest of central Italy. On this delicate mission he sends Andrea Orsini, his cousin Angela's lover and nearly as unscrupulous as himself. En route, Orsini meets Camilla Verano, wife of the count of Citta' del Monte (Borgia's next intended conquest); and sentiment threatens to turn him against his deadly master, whom no one betrays twice.