The Duke visits Mariana and is there when Isabella arrives. Isabella says that Angelo gave her two keys and instructions to meet him in a garden. Angelo showed her the way twice. She told Angelo that a servant will be accompanying her, thinking that she is coming to speak about her brother, so she cannot stay long.
Duke introduces Mariana to Isabella and tells them to discuss the plans together on their own. They go for a walk, and when they return they have agreed on the plan. Isabella tells her to say very little, but to be sure to tell him, "Remember now my brother," before she leaves. The Duke tells Mariana that she is not committing a sin, since she and Angelo had a contract of marriage.
Meanwhile, back at the prison, the Provost asks Pompey if he will help execute Claudio and another prisoner. If he does so, the charges against him will be dropped. Pompey agrees, and the Provost introduces him to Abhorson, the executioner. Abhorson says that Pompey will discredit the execution trade. Pompey agrees to be his helper, though, and Abhorson is told to be ready at four o'clock the next day.
The Duke arrives, and the Provost asks if there is any hope of saving Claudio. The Duke says that a pardon may arrive before morning. A messenger arrives, and the Duke says that it is probably the pardon, but it contains instructions to execute Claudio by four o'clock and Barnadine in the afternoon, and to send Claudio's head to Angelo by five.
The Duke asks who Barnadine is, and the provost tells him that he is a Bohemian who has been in prison for nine years. The Duke asks whether he is repentant, and the Provost says that he is as reckless and carefree as he has always been. The Provost says that he does not care that he is in prison, and has not been affected by news of his upcoming execution.
The Duke asks for Claudio's execution to be postponed four days. The Provost asks how he could do such a thing, considering the precision of Angelo's instructions. The Duke tells the Provost to send the head of Barnadine in place of Claudio's. The Provost argues that Angelo will notice it is the wrong person, but the Duke tells him to shave the head and beard of Barnadine's head to disguise it.Read a translation of Act IV, Scenes i-ii →
The Duke's schemes are developed more fully, and here we really see him directing his followers according to precise instructions. He tells Isabella and Mariana what to do with assuredness, although the plan could clearly fail, considering the intimacy of the proposed contact between Angelo and Mariana. The issue is not discussed clearly, nor is the question of why it is legal for the act to take place truly explored. After all, Claudio and Juliet had a similar contract of marriage to Angelo and Mariana's, and in that case both were willing. Here only one party is willing, and yet it is considered lawful. Perhaps it is the thought of tricking Angelo which makes the scheme seem appropriate here.
Mariana, when asked if she approves, answers that she will carry out the scheme if the friar thinks it is all right. The Duke assumed all along that Mariana would be willing to have sexual intercourse with Angelo, despite his hateful behavior towards her. The suggestion is that she can be redeemed only through this sexual act, because otherwise she remains a discarded woman instead of a wife.
The Duke also arranges a scheme involving the provost and the executions which are to take place. He is willing to sacrifice the life of Barnadine but wishes to preserve the life of Angelo. This implies a value judgment on life itself; one life is seen as worthwhile while the other is not. These statements of balance and equality figure largely in the play as a whole, as prospects are weighed against each other. The whole concept of "Measure still for Measure" (IV.i.414) centers around appropriate punishments and retributions.