In Amalfi, some years later, Antonio greets Delio, who has been away from court for some time. He informs Delio that he and the Duchess have had two more children. Delio asks if this news has reached the Cardinal, and Antonio responds that he fears it has, as Ferdinand has been acting strangely. The common people say that the Duchess is a “strumpet,” and they assume that Antonio has been getting rich dishonestly by stealing from the Duchess. They never even imagine that the two are married.
Antonio is afraid that Ferdinand knows about the births, because, despite Ferdinand’s claims that he would learn to be calm and do nothing until he had solid evidence of who the father is, Ferdinand has apparently been unable to completely conceal his fury. It’s also telling that the clues to Antonio being the father of the Duchess’ children are under everyone’s noses, but nobody suspects him—this points to the rigidity of the class structure.
Ferdinand, the Duchess, and Bosola then enter, and Ferdinand says that he’s going to bed. He suggests to the Duchess that she marry Count Malateste, but she says that he’s insufficient, and that if she marries again it will be for Ferdinand’s honor. The Duke tries to talk to Antonio, but the Duchess cuts him off, telling him that she wants to talk about the rumors that have been circulating about her honor. Ferdinand says he doesn’t want to hear it, but he assures her that even if the rumors were true, he would forgive her. She gives an aside of relief and then exits along with Antonio and Delio.
Here the Duchess pretends to take up the same argument that the Cardinal and Ferdinand made, namely that by marrying below her status she will bring dishonor to herself and to the family. She makes this argument in order to avoid having to marry, since obviously she has already married Antonio. Given Ferdinand’s threats, it’s also fairly obvious to the audience that his promise to forgive the Duchess if she has done anything against his wishes is preposterous.
Now alone, Ferdinand asks Bosola what new information he has. Bosola says that it’s rumored that the Duchess has had three bastards, but it’s unknown who the father is. Bosola suspects that someone has used sorcery to make the Duchess fall in love with them. Ferdinand asks if Bosola really believes in such potions, and Bosala says that he certainly does. Ferdinand dismisses these tricks as either lies or poisons that drive people insane. The only witchcraft, he says, is in the Duchess’s “rank blood.”
In another revelation about the play’s most complex character, we learn that Bosola believes in love potions. It’s unsurprising in light of his use of apricots to successfully induce the Duchess’ labor. When Ferdinand refers to the witchcraft in the Duchess’ “rank blood,” he uses “rank” here to mean disgusting, but it also refers to status.
After dismissing Bosola’s beliefs about potions, Ferdinand asks for a key to the Duchess’s bedchamber. Bosola asks Ferdinand what he intends to do with the key and then attempts to guess, but unsuccessfully. Ferdinand tells Bosola not even to try to figure it out, and he declares himself impossible to understand.
Even without Ferdinand’s sexual comments earlier in the play, his request for the key to the Duchess’s bedchamber would have struck audiences as extremely inappropriate. In a very theatrical moment, Ferdinand tries to keep Bosola (and the audience) guessing; he declares himself to be a mystery.