Claudio feels horrible about what he has just heard. He now feels responsible for Hero's death. He feels sorry about what he has done and wishes to make up for his mistake. So, he tells Leonato that he will accept any punishment that Leonato believes to be fair:
Impose me to what penance your invention Can lay upon my sin. (257-58)
The Prince also agrees to accept any punishment that Leonato sees fit. Leonato asks the two of them to inform all of the people of Messina about Hero's death, about how she died in purity and innocence (lines 265-66). Thus, Leonato's daughter and Leonato himself will have their honor restored. The reputation of his family name will once again be restored. In addition, Leonato asks Claudio and the Prince to mourn all night long at Hero's tomb. In this way, Leonato is testing them to see if their sorrow is genuine. But this night of mourning is also a punishment for the rash actions of Don Pedro and Claudio, who had ruined Hero's and Leonato's reputations.
Leonato then has one final "punishment" for Claudio. He tells Claudio that he has a niece who looks almost exactly like Hero herself, and this niece is now his heir. He then asks Claudio to marry this niece (even though Claudio has never seen her) to atone or to make amends for his sin. Claudio agrees.