Friar Peter has Mariana come forward, as the Duke urges Angelo to be judge of his own case.
Mariana says she will not show her face until her husband bids her to do so; she says she is not a maid, a widow, or a wife, and then tells them that she has slept with her husband, whom Isabella is accusing.
The Duke returns, greeting Angelo and Escalus by saying he has heard that they have done an outstanding job, and that Angelo should be praised for his good work.
He calls for Escalus and Angelo to walk with him, as he greets the people of the city.
Lucio gets angry at him for accusing him of saying bad things about the Duke, which in turn Lucio accuses the friar of; then, Lucio pulls off the ' Friar's' disguise and finds that it really is the Duke after all.
Angelo then knows that he is undone; he says he will confess what he has done, and forego a trial of his wrongdoing.Isabella then kneels before the Duke, and asks to be heard so that she can claim justice.The Duke urges her to speak, and to address Angelo with her grievance, since he is one that can give justice to her.The theme of justice is also apparent, as Angelo will have to judge his own guilt here, as the Duke says he should.However, Angelo has become no more just than he ever was, and has not learned of moderation in justice either; he tries to cover up his wrongs by trying to silence justice, which luckily, he does not get away with.He does this for no reason other to have her be very happy, and perhaps look even more just and heroic, when it is revealed that he actually saved Claudio's life.The Duke did his duty as a ruler, seeing to it that justice was kept and no undue sentence performed; however, through this public performance of accusation, repentance, and grief, he shows the extent of his power, and makes himself look even more just, important, and beneficent since he appears to have single-handedly acquired justice for everyone.The Duke then says for Claudio to be reunited with Juliet, and for Mariana and Angelo to live happily.He calls Isabella to him, since they are to be joined, and calls the play to a close on a 'happy' note.She tells the story of the contract between herself and Angelo, and that she slept with him in place of Isabella.Angelo admits that he broke off a marriage contract with her, but was justified in doing so; Mariana begs the Duke for mercy, but Angelo says that he thinks these women are being manipulated, and should be punished for their testimony.