The Duke doesn't want to look like a mean ruler and he feels that Angelo is strict enough to be perfect for the job but the Duke secretly stays in Vienna disguised as a friar to see how things go.

To everyone's surprise including the Duke's, Angelo carries his harshness a little too far. This becomes apparent when Claudio is given a death sentence for getting his fiancée, Juliet, pregnant before they were married.

This is when Isabella, a novitiate entering a nunnery and Claudio's sister, steps in to beg Angelo for her brother's life.

Angelo won't hear anything of it but Isabella's beauty and virginity stirs him and so he tells Isabella that he will trade Claudio's life for Isabella's virginity to be given to him. Isabella's virginity is her honor and her life, especially because she is becoming a nun but she tells Claudio any way and Claudio will not have his sister trade her virtue for his life. The Duke hears of the situation and plots a plan to save Claudio and Isabella from his deputy, Angelo.

Enter into the play, Mariana. Mariana who was once engaged to Angelo and is still madly in love wih him is asked by Duke Vincnetio to do him a favor. The Duke then persuades Isabella to pretend to accept Angelo's offer of trade, her brother's life for her virginity and when the sparks start to fly, Mariana and Isabella will switch places in the darkness.

The plan works but Angelo does not keep his part of the bargain and decides to have Claudio killed anyway.

When Duke Vincentio, still disguised as a friar, hears that Claudio is to still be executed, he convinces the jailer to substitute another condemend man for Claudio and to carry out his orders as he would have with Claudio.

The Duke also tells Isabella of Angelo's betrayal and that she should seek justice from the Duke who is expeted to return shorty. Duke Vincentio then goes away to change out of his disguise so he can confront Angelo.

Isabel and Mariana arrive and make many true accusations against Angelo to the Duke. Angelo tells the Duke that Isabella is a liar and that a friar is also to blame. Duke Vincentio then reveals himself to be that same Friar and Angelo throws himself at the mercy of the Duke and Isabella both. The Duke then reveals that Claudio is still in fact alive and that because Mariana pleads for Angelo's life that Angelo must marry Mariana and that Claudio and Juliet should marry hastily and then finally, Duke Vincentio and Isabella also get married.