Duke Vincentio has given his deputy Angelo temporary power over Vienna before his leave for a diplomatic mission. But instead of leaving the city, the Duke disguises himself as a friar named Lodowick, and stays behind to observe the city's happenings and Angelo's brief reign.Meanwhile, Angelo decides to enforce the laws on prostitution and debauchery, effectively shutting down the red-light district. A man named Claudio gets arrested for impregnating his lover, and Angelo sentences him to death. Claudio's sister enlists a certain friar's help to trick Angelo into releasing her brother.