Two Changes: One of Vindice and One of Form

Brother that's I: that sits for me: do you mark it.  And I must 

stand ready here to make away myself yonder; I must sit to

be killed, and stand to kill myself       (IV.iv.4-6)

These lines stand out to me for two reasons.  One, Vindice is expressing an awareness of his own possible end in his revenge plot.  When he points to the Duke's corpse dressed in Piato's clothing and states, "that's I,"  he's alluding both to the costume and his (Vindice's) death.  Acting in revenge, Vindice acknowledges that to enact his vengeance he may also have to die.  Second, Middleton switches to prose at the beginning of this scene.  I think this change has something to do with Vindice's acknowledgement.  Now that Vindice has vocalized his realization that his plot will end in his own end, the action of the play has reached its climax.  I believe that this change to prose signals the importance of Vindice's words.