The Cardinal is in his chambers, holding a book and questioning what hell is like from a scholarly perspective. As he laments the pains of a guilty conscience, Bosola and the Servant enter with Antonio’s body. The Cardinal comments that Bosola looks terrible, somehow both determined and fearful. Bosola responds that he has come to kill the Cardinal and draws his sword. The Cardinal begins to howl and yell, and he offers to pay Bosola, but Bosola refuses. Then the Cardinal tries to call the courtiers again; upstairs in the palace, the courtiers hear the Cardinal’s cries. Most of the courtiers decide to follow the Cardinal’s orders and not intervene, but Pescara finally decides that the Cardinal doesn’t sound like he’s joking, and goes to investigate.
The Cardinal is now so consumed with guilt that he is checking his scholarly books to better understand what his future in hell will be like. Bosola proudly (and somewhat foolishly) announces that he’s there to kill the Cardinal, but the courtiers are so afraid of disobeying the order to stay away that they do not come to the Cardinal’s aid when called. Only Pescara, who has been shown as truly honorable and noble, is willing to risk disobeying to see what’s truly happening.
Bosola kills the servant to make sure no one will unlock the door to the Cardinal’s room. He then admits to the Cardinal that he slayed Antonio by mistake. Bosola stabs the Cardinal twice, at which point Ferdinand enters after hearing the commotion. The Cardinal asks his brother for help, but Ferdinand mistakes him for the devil, and he stabs both the Cardinal and Bosola. The Cardinal cries out that sorrow is “the eldest child of sin.” Ferdinand says that Caesar had a better fortune then Pompey, since Caesar died in prosperity while Pompey died in disgrace. He says that the Cardinal and Bosola are now splendid men since they’re and dying in the field of battle. He concludes by saying that pain is nothing, and that often one small pain is taken away by the apprehension of a greater one. After Ferdinand states this philosophy on pain, Bosola takes the opportunity for revenge and fatally stabs Ferdinand.
Bosola’s murder of the servant seems excessive, but, given the servant’s low class, the play pretty much skips over that death. When Ferdinand enters to help, he is by now so insane that he (somewhat ironically) mistakes the Cardinal for the devil. The Cardinal’s exclamation continues to echo the sentiment that sorrow and misery are bred by our own sins. Ferdinand seems at once lucid and insane. His lines about Caesar and Pompey seem to suggest he feels some glory in dying in battle, and his philosophy on pain might suggest that his apprehension of dying and going to hell is enough to take away his pain from guilt, thereby figuring death once more as an escape from a life of pain.
Ferdinand, gravely wounded, says that the world is a no better than a dog kennel, and he says that he’ll ignore his reputation and hope for “high pleasures beyond death” (i.e. that he will go to heaven). He then cries out for the Duchess, and says “whether we fall by ambition, blood, or lust, / Like diamonds we are cut with our own dust,” and dies. Bosola says that he is himself on the verge of death just as Pescara, Malateste, Roderigo, and Grisolan enter and ask what’s going on. Bosola explains that he has taken revenge for the Duchess of Malfi, who was murdered by the brothers, as well as revenge for Antonio (who was murdered by mistake) and Julia (who was poisoned by the Cardinal). Finally, he says, he has taken revenge for himself, who was an actor involved with everything, but against his better nature. The Cardinal explains that Ferdinand wounded them, then prays that they never think of him (the Cardinal) again, and dies.
After his half insane ramblings, Ferdinand turns to religion, cursing the painful earth and hoping to go to heaven despite his bad actions. His fate, though, he says with his final words, is undoubtedly caused by his own actions and sins. We can note that Bosola claims revenge for murders he committed himself at the behest of the Cardinal and Ferdinand. He justifies this seeming hypocrisy by saying that he wanted revenge since he was forced into his role despite his good nature, once more using a meta-theatrical notion that he is an actor in a play. At the end of his life the Cardinal is able to pray again, but only to be forgotten, not forgiven, which does not bode well for his salvation.
Pescara comments on how the Cardinal prevented his own rescue, and Malateste calls Bosola a “wretched thing of blood” and asks how Antonio died. Bosola says Antonio died “in a mist,” as a way of describing the confusion of that moment, then says he has often seen mistakes such as Antonio’s death in plays. Bosola cries out that he is dying, and laments the state of the world he will leave behind. Before dying, he says, “let worthy minds ne’er stagger in distrust / To suffer death or shame for what is just: / Mine is another voyage.”
Pescara notes the unfortunate irony of the Cardinal’s death, and Malateste’s comment recalls Shakespeare’s Coriolanus. Bosola’s explanation of Antonio’s death is a final, overt meta-theatrical moment; he says that the mistake was something only seen in plays. With his final lines he emphasizes the importance of honesty and acting in accordance with one’s moral values.
Delio then enters, too late, with Antonio’s eldest son and heir. Delio says that he was prepared beforehand for what happened, and he hopes to get the young boy his inheritance. He hopes, too, that the famous, powerful brothers and their horrible deeds are forgotten like footprints in melting snow. Delio ends the play by remarking that he has always believed that nature best serves great men only when it makes them “lords of truth.” He then says that integrity is the best friend of reputation, as it has the noble power to outlast even death.
While plays of this era often end with a speech from the highest-ranking character, the deaths in this play are so prolific that they leave a power vacuum; the entire ruling class has perished. Delio closes by giving value to the one virtue that seemingly everyone in the play lacked: integrity and honesty. While some merits might not always lead to tangible benefits, the play seems to suggest that truth and integrity will be rewarded after death.