Prince of Foxes(1949)

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