It is sunset and time for Horatio and Bel-Imperia's rendezvous. Horatio, Bel-Imperia, and Pedringano enter Hieronimo's garden. Bel-Imperia sends Pedringano to keep watch and alert the pair if anyone approaches; instead, Pedringano goes off to inform Lorenzo and Balthazar of the two lovers' whereabouts. While he does this, Horatio and Bel-Imperia talk, first flirtatiously, then seductively, about their growing love. However, just at the second the two are about to "stop talking", Pedringano returns with Lorenzo, Balthazar, and Balthazar's manservant Serberine, who hang Horatio up on a tree (or a tree-covered treliss, "arbour" can mean both) and then stab him several times for good measure. The drag Bel-Imperia away kicking and screaming, as she cries out for Hieronimo's help.
Hieronimo, awakened by screams, runs into his garden to discover a man hanging from one of his trees. Only after cutting the man down does he recognize him by his clothes as his son, Horatio. He cries out in anguish, begging his son to speak if he lives, soon realizing that he has died. His wife Isabella, disturbed by his absence from their bed, discovers the horrifying scene and begins to cry out in grief. Hieronimo takes a bloodstained handkerchief from his son and vows to wear it until he takes revenge on his boy's murderers. He and his wife then carry away their son's corpse, with Hieronimo briefly considering suicide, then rejecting it in favor of revenge.
Andrea is now very upset with Revenge. Not only has he failed to see Balthazar killed, as he had hoped; he has instead been forced to witness the murder of his friend Horatio. But Revenge promises Andrea that he is premature in his condemnation and that, in due time, Balthazar will suffer vengeance.
The murder of Horatio is the play's first turning point and the culmination of the initial rising action we have just seen. In effect, the main plot up until this point has centered around Bel-Imperia's desire to revenge Andrea against Balthazar, and Balthazar's counter-desire to revenge himself against both Bel- Imperia and Horatio. From now on, these revenge motives will disappear, and the main plot will now be driven by Hieronimo's desire to seek justice for his son, his increasing madness, and his eventual bloody revenge. This shift in protagonist also reflects a shift in the play's central theme, from that of simple revenge to revenge as a form of justice.
The tragic protagonist is characterized by psychological complexity or an interiority that is frequently conflicted both with itself and with the world around it. This interiority often expresses itself in a question or series of questions that the protagonist must address, a series of internal struggles with which the protagonist must deal. Kyd uses a series of soliloquies to give us access to this interiority, and the first one comes in II.v, with the discovery of his son's body. His question is simple and direct: how can the world be so unjust as to let his son be murdered and to let the murderers of his son go unpunished? Hieronimo expresses his anguish over the seeming injustice of the world by using apostrophe (the addressing of inanimate objects) in succeeding rhyming couplets: "'O heavens, why made you night to cover sin? O earth, why didst thou not in time devour / The vild profaner of this sacred bower?" But Hieronimo's anguish is answered by Isabella's faith that the murderers will be exposed: "The heavens are just, murder cannot be hid, / Time is the author both of truth and right," she says, and this could be taken as the play's optimistic premise, the hope that with the passage of time, justice will be done.
The equation between revenge and justice on the one hand and simple relief on the other also becomes important. "To know the author were some ease of grief, for in revenge my heart would find relief." But another source of relief is readily available: that of suicide. Hieronimo only explicitly mentions this possibility in the Latin section at the end of the scene: "Emoriar tecum: sic, sic juvat ire sub umbras./At tame absistam properato cedere letho," (I will die with you: thus, thus it will please me to go to the shades below / But however I will refuse to hasten my death). He refuses the option of suicide because to do so would mean that Horatio's death would pass unavenged. Revenge is thus not a means solely for Hieronimo to satisfy his own longing for retribution: it is something necessary because it is only just that Horatio's death should be revenged. This emphasis on justice is not something that was present in Andrea's vengeful speeches or in Bel-Imperia's.