Near the shrine, Antonio, the Duchess, their children, Cariola, and a few servants have been banished from Ancona. Antonio notes that their group has been vastly reduced in size, since most of the staff have found other opportunities since the banishment. The Duchess says that she had a strange dream that she wore her coronet of state, but the diamonds were changed to pearls. Antonio interprets the dream, saying that he believes the pearls signify tears, which suggests that the Duchess will soon be forced to weep.
Most of the servants and courtiers attending the Duchess have abandoned her, since what they really wanted from her was social and financial advancement. Since her banishment makes that impossible, they’ve found other jobs. Antonio rightly interprets the Duchess’s dream, which foreshadows the misery and suffering that are about to unfold.
Bosola then enters with a letter from Ferdinand that is supposedly “all love and safety.” But the Duchess immediately calls Bosola out for describing the letter in this way, saying that it’s just a calm before the storm, and that false hearts speak kindly to those that they are about to hurt. Though the letter asks for a meeting with Antonio, both the Duchess and Antonio assume that Ferdinand actually wants Antonio dead. Antonio thus refuses the invitation; he will not see the Duke and the Cardinal until he’s certain that they are placated and will not harm him.
Like Ferdinand’s comment that the Duchess is most foul when seeming most pure, the Duchess believes that her brothers are merely attempting to seem nice before killing Antonio. The brothers have apparently become less and less skilled at concealing their true selves by this point in the play.
Bosola exits, and the Duchess says that she is afraid there will be an ambush. She tells Antonio to take their eldest son to Milan, using an expression equivalent to “let’s not have all our eggs in one basket.” She says that she isn’t sure what’s worse, seeing Antonio dead or parting with him, and she bids her son farewell, saying that he’s happier for not understanding what’s happening, since wit just brings a truer understanding of sorrow. Antonio tells her not to weep, as heaven fashioned them out of nothing, and they are moving towards an eventual reunion in heaven. The Duchess notes that his speech sounds like that of a father on his deathbed, and Antonio and their son exit.
Antonio and the Duchess split up the children in the hopes that some of them will survive. She plays on the trope that parting with the beloved is akin to death, and she essentially tells her son that ignorance is bliss, slightly echoing Bosola’s comment that wisdom leads only to folly. Antonio uses an appeal to faith and the afterlife in order to calm the Duchess down and provide the family with hope. The Duchess, though, seems to know that she’ll never see her husband again in this life.
As soon as Antonio leaves, the dejected Duchess finds herself facing a disguised Bosola and several troops. Bosola says that she is not to see her husband anymore, and she questions who he is to act like a god. He responds that he is taking her to her palace, not a prison. The Duchess says that Charon’s boat brings the dead across the river Styx into Hades and brings no one back, which implies that she knows that she will never leave the palace again. Though Bosola claims that her brothers want to keep her safe, she does not trust them. Bosola asks about her children, to which the Duchess replies that if she were a man, she’d beat Bosola’s mask into his face.
The Duchess’s references the mythology of Hades suggest both that she knows she is about to suffer, and that she knows her she will soon be imprisoned, even if she is just being confined to her palace. She continues to express independence and frustration with social mores, saying that she’d strike Bosola if she were a man. While she is able to invert the courtship tradition, she’s unable to fully subvert her role and physically overpower Bosola.
When Bosola tells the Duchess to forget Antonio because of his low birth, she responds by telling an story about a salmon that swims into the sea and meets a dogfish, who asks the salmon why it is so bold as to enter the esteemed waters of the ocean, since salmon only live in shallow rivers with shrimps. The salmon responds first with thanks that both of them have not been captured by fishermen, and says that their value cannot truly be known until they’re caught and sold in the market; the salmon’s price might be higher than the dogfish’s, even though that just makes the salmon closer to being eaten. The moral of the story, the Duchesss says, is that men are often valued when they are most wretched. After her speech, she agrees to go with Bosola (though she doesn’t really have a choice).
The Duchess’s story about the salmon is an allegory about social class. The salmon appears to be lowly when going from a river to the ocean, but in the fish market, it might be valued more than an ocean fish. The story has two implications. First, that it’s not always obvious what kind of fish (or person) is most valuable. Second, a good value might not always be what it seems, as the higher value in the fish market just means the fish is more likely to be eaten. All of this is to say that society makes the mistake of placing emphasis on class and valuing despicable people like her brothers.