Virgílio alerts Catarina to the loyalty that Cássio has to Afonso. Afonso advises Diana to be careful with Catarina. Catarina manipulates Rodolfo, making him suspect that Cássio may be influencing the people against him. Cássio feels offended by Rodolfo's accusations and gives up his position as advisor and army commander. Afonso tells Amália that he will not leave Montemor.