Act 4, Scene 1
Bellimperia berates Hieronimo for his inaction thus far: why has he neglected to avenge his son's murder? Hieronimo excuses himself, stating that he was previously unsure as to whether Bellimperia's letter contained the truth. For him, Bellimperia's desire for revenge now represents a sign from heaven: "all the saints do sit soliciting / For vengeance on those cursed murderers." He declares his resolve to exact revenge, and Bellimperia agrees to help him carry out his plot.
Balthazar and Lorenzo arrive, asking Hieronimo to provide the night's entertainment for the King. The Marshall readily agrees. A play that he wrote in his youth shall be performed - by none other than the two men, Hieronimo himself, and Bellimperia. The plot involves a knight and his wife Perseda, the Turkish emperor Soliman, and one of his Bashaws. Hoping to arrange a marriage between Soliman and Perseda, the Bashaw kills the knight. In retribution, Perseda kills Soliman and then commits suicide. Hieronimo will play the Bashaw, Balthazar will be Soliman, Lorenzo will act the knight, and Bellimperia, naturally, will play Perseda.
Balthazar calls for a comedy instead, but Hieronimo rejects the suggestion. He moreover stipulates that each character should speak in a different language. The play will thus be performed in Latin, Greek, Italian, and French. Balthazar once again objects, stating that such a mixture would only result in confusion. To this, Hieronimo promises that he will deliver an oration - and reveal a surprise - that will resolve everything in the last scene.
Act 4, Scene 2
Isabella stands at Horatio's deathplace, weapon in hand. Seeing that "neither piety nor pity moves / The king to justice or compassion," she vows to avenge herself on the very spot where her son was murdered. She cuts down the arbor where Horatio was /'/hanged and delivers a soliloquy, cursing the garden and apostrophizing Hieronimo before stabbing herself.
Act 4, Scene 3
Hieronimo enters with the Duke of Castile, who surveys Hieronimo's earnest preparations for the evening. Upon Hieronimo's request, the Duke agrees to give the king a copy of the play, as well as toss Hieronimo the key to the gallery once the royal train has entered. Balthazar passes through briefly to help with the setup. Alone on stage, Hieronimo prepares himself mentally for the evening:
Bethink thyself, Hieronimo,
Recall thy wits. . .
The plot is laid of dire revenge
On, then, Hieronimo, pursue revenge;
For nothing wants but acting of revenge. (IV.iii.22-30)
Act 4, Scene 4
The King arrives with the Viceroy and the Duke of Castile. The King hands the Viceroy a copy of the play, translated into English for easier understanding. The play is performed as previously summarized by Hieronimo. Hieronimo's character stabs Balthazar's, after which Bellimperia's character stabs Lorenzo's and herself. The play ends to the enthusiastic applause of the King and the Viceroy. Hieronimo then delivers the final speech: while the play may have seemed "fabulously counterfeit," he explains, it was in fact a very real spectacle. Hieronimo reveals Horatio's corpse on stage (presumably by lifting the curtains, of which he previously spoke) and declaims his accomplished revenge scheme, as well as his motives therein. Finally, "Hieronimo / Author and actor in this tragedy" runs to hang himself.
The King and the Viceroy break the locked doors and rush to detain Hieronimo. Along with the Duke of Castile, they demand to know Hieronimo's motives for orchestrating the murders. Hieronimo says in few words that he sought revenge for his son, then refuses to speak any more on the subject. The King calls for torturers, but Hieronimo bites out his tongue. The King and the Duke insist that he can still write. Hieronimo gestures for a knife to mend his pen, with he uses to stab both the Duke and himself. The King and the Viceroy exit in mourning.
Act 4, Scene 5
The Ghost declares his desires satisfied. He arranges with Revenge to have Bellimperia and Horatio treated well; in contrast, Lorenzo, Balthazar, Serberine, and Pedringano will be sent to the worst parts of hell. The two return to the underworld with Revenge's last words:
Then haste we down to meet thy friends and foes:
To place thy friends in ease, the rest in woes;
For here though death hath end their misery,
I'll there begin their endless tragedy. (IV.v.45-48)
Analysis
After the lengthy third act, almost all the loose ends of the play have been tied up. The wheel of fate is once again set in motion: all that remains is for Hieronimo's play to be staged. First, however, Isabelle commits suicide in the second scene. Readers as well as producers are faced with the question of how to interpret the scene: when she sets out to take revenge on nature, cutting down the arbor where Horatio was hanged, has she gone completely mad? Her earlier signs of lunacy suggest a positive answer. But it may be an oversimplification to reduce her actions to "madness" as such, for to do so is to bereave her suicide of rationality or meaning.
Isabella's suicide, in fact, emerges out of a logic entirely consistent with her earlier words. In Act 3 Scene 8, she expresses a longing for Horatio that is forgotten - or overridden - by her desire to find his murderers. It is unclear whether Hieronimo has told her of Lorenzo and Balthazar by the fourth act. In any case, Isabelle would be powerless to take revenge on the two young men. All she can do, then, is to "revenge [her]self upon this place" where Horatio met his untimely death. It is a gesture of protest, indeed a denial of any further life in a place that is testament to her son's death: "Fruitless for ever may this garden be, / Barren the earth." Her own suicide also can be understood in a similar manner. Apart from joining her son in death, Isabella's suicide is also designed to prevent herself from engendering further life: "as I curse this tree from further fruit, / So shall my womb be cursed for his sake." She, too, is part of nature; she, too, will join nature in death.
As for Hieronimo's plot, it unfolds exactly as envisioned. Just like Lorenzo, it seems, the Marshall has the gift of dissimulation and manipulation. The play itself is simple in plot, but is nonetheless intriguing. Why should it be written in four languages? Hieronimo declares at the end of the first scene: "Now shall I see the fall of Babylon, / Wrought by the heavens in this confusion." The phrase is dramatically ironic, insofar as Revenge has been working invisibly to create confusion - and doubly ironic, insofar as Revenge represents hell rather than heaven. In context, "the heavens" also points to Hieronimo himself. He has the equivalent of divine authority in the righteousness of his murder, as well as in his authorship (author derives from the Latin auctor, or "authority"). He is the chef d'orchestre, as it were.
As for the representation of Babel itself, the choice is appropriate. Babylon was one of the largest cities of the ancient world, believed to be both luxurious and corrupt. It was there that the Tower of Babel was built so high as to menace the heavens, and it was there that God punished mankind for its arrogance, spreading linguistic confusion all over the world (see Genesis 11:1-9). Balthazar and Lorenzo would make model citizens of mythical Babylon, as they are rich, powerful, and corrupt. Bellimperia herself bears the unfortunate name of Bellimperia - beautiful and powerful. They are all testament to the confusion that mankind brought upon itself through the love of wealth and power.
To the King, the play is once again like a dumb show. He requires an English translation to comprehend it, and even then he does not understand that the "fabulously counterfeit" stage is not so counterfeit after all. He cannot grasp the meaning of Horatio's corpse on stage. Just as with the dumb show in Act 1 Scene 5, Hieronimo must explain its significance - which he does at some length. But curiously, no members of the royal audience seem to understand his explanation. The King, the Viceroy, and the Duke all frantically demand to know his motives:
King. Speak, traitor. . . speak!
. . .
Vic. Why has thou murdered my Balthazar?
Cast. Why has thou butchered both my children thus? (IV.iv.164-168.)
Hieronimo recapitulates his motives in eight lines of "good words," but even then the three men are not satisfied.
Why, then, does Hieronimo refuse to explain in greater detail the events that led up to the play-within-a-play? Perhaps his silence constitutes a form of extended revenge. The death of Horatio caused both him and his wife tremendous sufferance. By refusing to reveal the full history behind the tragic play-within-a-play, Hieronimo extends the same sufferance to the fathers of Balthazar and Lorenzo. The King, of course, does not fit into this interpretation, but Hieronimo has also gone to extremes bereft of common sense - or, for that matter, any sense: after biting out his tongue, he stabs the Duke of Castile before committing suicide. In one short scene, he has destroyed the future hopes of Spain and Portugal. Has justice been served? Was his revenge justified? Is revenge ever justified? All strife on earth, in any case, has come to an end: all characters that could potentially further the cycle of revenge have died. But as Revenge notes, the end is only the beginning of more pleasure and pain. It is up to the audience to decide whether his hell is not merely a figure for reality outside the theater.