In prison, Vincentio continues to pose as a friar and comforts Claudio about his impending execution by reminding him that all mortal life is temporary and that death is inevitable. Isabella comes to visit her brother and Vincentio hides to eavesdrop on their conversation. She reveals to Claudio that Angelo will only spare his life if she gives him her virginity. Claudio initially condemns this plan and considers it unethical, but as he contemplates the terrifying uncertainty of the afterlife, he changes his mind. Enraged that her brother would ask her to commit a sin to save him, Isabella leaves. Vincentio, still disguised as a friar, tells Claudio that Angelo intends to have him executed no matter what and that he is likely only offering Isabella this bargain to test her virtue. Claudio regrets his moment of cowardice and plans to ask for his sister’s pardon.

Before Isabella leaves the prison, Vincentio speaks with her as well. He informs her that Angelo was previously engaged to marry a woman named Mariana, but he renounced her when her brother died in a shipwreck and she was unable to raise the money for a dowry.