"Vindicta mihi! Ay, heaven will be revenged of every ill, Nor will they suffer murder unrepaid: Then stay, Hieronimo, attend their will, For mortal men may not appoint their time. 'Per scelus semper tutum est sceleribus iter.' Strike, and strike home, where wrong is offered thee; For evils unto ills conductors be, And death's the worst of resolution. For he that thinks with patience to contend To quiet life, his life shall easily end. Fata si miseros juvant, habes salutem; Fata si vitam negant, habes sepulchrum.' If destiny thy miseries do ease, Then hast thou health, and happy shalt thou be; If destiny deny thee life, Hieronimo, Yet shalt thou be assured of a tomb; If neither, yet let this thy comfort be, Heaven covereth him that hath no burial. And to conclude, I will revenge his death!"

Hieronimo is the speaker (III.xiii.1–20), and in this soliloquoy he decides that he will personally revenge the death of his son (the "his" referred to in line twenty). This decision comes after he has failed to draw the King's attention to his case, thanks in part to the tactics of Lorenzo. He begins his deliberation by quoting the biblical injunction against revenge: "Vengeance is mine; I will repay, sayeth the lord" (Romans.xii.19). But he rejects this religious attitude, drawing on several quotations from the Roman playwright Senenca. He holds a copy of Seneca in his hand, and reads several quotations; the first is an observation that the safest way to cover up a crime is through more crime, the second an observation that the worst that can await a bold man is death. And that with death comes Heavenly reward-if one's cause is just. These seem to be the reasons Hieronimo decides that he must revenge his son. To do this, he will pursue Machiavellian tactics reminiscent of Lorenzo. Some critics have interpreted this as Hieronimo's shift from hero to villain. But others have seen it as consistent with his quest to dispense justice, especially since his two son's murderers are both in positions of extreme power and influence in Spanish society. This makes them both impervious to other forms of justice and liable to use their power to spread further evil.