The aim of tragedy, Aristotle writes, is to bring about a "catharsis" of the spectators — to arouse in them sensations of pity and fear, and to purge them of these emotions so that they leave the theater feeling cleansed and uplifted, with a heightened understanding of the ways of gods and men. This catharsis is brought about by witnessing some disastrous and moving change in the fortunes of the drama's protagonist (Aristotle recognized that the change might not be disastrous, but felt this was the kind shown in the best tragedies — Oedipus at Colonus, for example, was considered a tragedy by the Greeks but does not have an unhappy ending).
The plot of the tragedy mirrors the plot of the play as a whole (a sultan is driven to murder a noble friend through jealousy over a woman). Hieronimo casts himself in the role of the hired murderer. During the action of the play, Hieronimo's character stabs Lorenzo's character and Bel-Imperia's character stabs Balthazar's character, before killing herself. But after the play is over, Hieronimo reveals to the horrified wedding guests (while standing over the corpse of his own son) that all the stabbings in the play were done with real knives, and that Lorenzo, Balthazar, and Bel-Imperia are now all dead. He then tries to kill himself, but the King and Viceroy and Duke of Castile stop him. In order to keep himself from talking, he bites out his own tongue. Tricking the Duke into giving him a knife, he then stabs the Duke and himself and then dies.