This complex revenge tragedy involves the central character Vindice who acts as something of a vigilante in this drama, disguising himself to test the true goodness of various characters. In Act IV scene 4, Vindice and his brother, Hippolito, confront their mother, Gratiana, whom he has previously approached in disguise about prostituting her daughter, Castiza, to the Duke's son. Vindice now without disguise confronts his mother with the terrible nature of her actions and forces her to see the wickedness of her deeds. Vindice explains to his shocked mother how he knows of her evil nature, as he describes how he disguised himself as the Duke's servant and approached her about prostituting her daughter:
In that disguise I, sent from the Duke's son,
Tried you, and found you base metal,
As any villain might have done.
What is key in this speech is the way that Vindice sees his role as "trying" various characters through whatever means to discover if they are "base metal" or of more precious value. It is interesting that Castiza, later on in this scene, does exactly the same thing to her mother, pretending to have reconciled herself to the need to prostitute herself, in order to test her mother's character. This scene in the play therefore helps the audience to understand the characters better by exploring how Vindice sets himself the task of unmasking corruption and evil in the Venetian court through disguise and deception. Gratiana, when confronted with her evil, is at least able to repent and change her ways, which is of course something that other characters are unable to do, and therefore are punished by the self-appointed vigilante of Venice, Vindice.