
Mistress Overdone runs a brothel in Vienna's suburbs and appears first bearing news of Claudio's arrest, gossip she delivers with the same practical, transactional interest she brings to her own business - Claudio's fate is, among other things, information relevant to her trade. She has, by her own count, survived nine husbands and considerable turnover in her business, giving her a weary, long-practiced resilience toward Vienna's shifting moral enforcement.
A bawd whose brothel business is threatened by Angelo's crackdown on vice, and whose arrest in Act III is reportedly the result of Lucio's own information against her.
Angelo's crackdown threatens her livelihood directly, and Pompey's prediction that the city's houses of resort will need to close proves accurate in her case: she is arrested in Act III, reportedly on Lucio's own information against her, an irony given his frequent patronage of exactly the trade he is credited with helping suppress.
Mistress Overdone does not appear in the play's final scene, her fate left unresolved along with the broader question of what becomes of Vienna's vice trade once Angelo's brief, hypocritical crackdown gives way to the Duke's restored, presumably more moderate rule.
Mistress Overdone is motivated by simple economic survival, adapting as best she can to a legal crackdown that directly threatens the trade she has practiced through nine husbands and considerable turnover in business.
Mistress Overdone brings a weary, long-practiced pragmatism to news that would alarm a more sheltered character, treating Claudio's arrest and Angelo's crackdown alike as simply the latest shift in a trade she has weathered changing fortunes in for years.