First things first. It's a tragedy, meaning that there pretty much had to be mass death at the end of the play. So from the beginning, Kyd's original audience would've known that Hieronimo had to die because he's the tragic hero. And it makes sense that Lorenzo and Balthazar had to die because they were the worst dudes in the play.
But why did Bel-Imperia have to die? And why did her father, the Duke of Castile, have to die? And why did the play go out of its way to have everyone die while performing as actors in a play-within-a-play? These are the head scratchers of the ending. And Shmoop is here to cure that itch. Or at least to get you scratching.
Waiter, There's a Play in my Play
The play-within-a-play is a common convention in Elizabethan drama. Professor types call plays-within-plays moments of metatheater. Pretty fancy word, huh? Metatheater means that a play is having fun with its audience members by reminding them that they are watching a play.
The magic of watching plays and movies is that we find ourselves forgetting we're in a fictional world. This is why you cried when that big, mean fish ate Nemo's mom and all her eggs (except Nemo) in Finding Nemo. Ready for a little cry?
If you didn't cry, go to the doctor and see if you still have a heart. If you did cry, it's because you allowed yourself, however briefly, to get lost in another reality. Well, when Renaissance playwrights used plays-within-plays, they wanted to snap you back into thinking you're just watching a play.
Why would they do this? To get you thinking critically about theater itself, that's why. So, the effect of staging a bloodbath in a metatheatrical way might be about getting the audience members to think about why they pay money to watch murder portrayed in a realistic way. On that note, why do so many people love watching Dexter, or CSI, or slash-and-gash horror films? Think about that.
Maybe the tragedy ends with a play-within-a-play to get people thinking about how murder is an inherently theatrical performance? Or that following the path of revenge changes one's character (so to speak) for the worse? We'll leave the answers to these questions up to you.
Flipping the Script
But while you're thinking about all this, consider why Bel-Imperia deviates from the script by killing Balthazar and herself. As Hieronimo makes clear, Bel-Imperia does not play her part as he intended when he wrote the play:
Poor Bel-Imperia missed her part in this.
For, though, the story saith she should have died,
Yet I of kindness and care to her did
Otherwise determine her end. (4.4.140-143)
Hieronimo's saying that the original story he borrowed from had Isabella's character die, but that he cared for her so much he rewrote the end for her. Does this mean she was fated to die no matter what? Or that there is some original script (or fate) out there that none of us can control? Or does it mean that playwrights cannot control human forces even in plays, try as they might? Are we living in a wildly uncontrollable world where human emotion constantly flips the script? Could be, could be.
Or maybe it's simply that revenge is an uncontrollable force that swallows up even the innocent. Maybe that's why the Duke of Castile has to die. Castile did everything he could to make sure his malignant son didn't harm Hieronimo. And yet Hieronimo stabs him to death with a pen. Maybe revenge can't stand as true justice, because once someone takes an eye for an eye, then another person goes eyeball hunting, and on and on till there are no more eyeballs. There are so many ways you can go with the ending, so set your eyes on the prize and express what you think.