
Angelo receives the deputation of Vienna's government with evident reluctance, stating that his character has not been sufficiently tested for such trust - a caution that proves prophetic. His first acts as deputy are severe: he revives the dormant law against fornication and sentences Claudio to death for conceiving a child with his betrothed before their marriage contract was formally sealed, refusing Escalus's plea that he weigh his own hypothetical guilt under equally strict scrutiny.
The Duke's deputy, whose strict enforcement of Vienna's laws against fornication collapses into abuse of power once he desires the very virtue he condemns in others.
His encounter with Isabella unbalances him completely. Her plea for her brother's life, made with a moral clarity Angelo has spent his life cultivating in himself, produces not admiration but desire, and he is startled to find his professed virtue has no defense against it. He propositions her directly - her body for her brother's life - and when she threatens exposure, calmly informs her that his reputation guarantees no one will believe her.
Angelo's downfall follows a logic he cannot escape: believing the bed-trick has secured Isabella's compliance, he orders Claudio executed anyway, and only the Duke's counter-scheme prevents an actual death. Unmasked publicly in Act V, Angelo confesses without much resistance, requesting death rather than mercy - a final rigidity the Duke overrules by sentencing him to marry Mariana instead.
Angelo is motivated first by a genuine, if untested, commitment to strict lawfulness, and then, once Isabella's virtue provokes an unexpected desire in him, by a need to satisfy that desire while preserving the reputation his authority depends on.
Angelo's severity is not simple villainy but the brittleness of a man who has never been tested - his soliloquies show him genuinely startled by his own desire for Isabella, unable to reconcile it with the self-image his authority has been built on. His hypocrisy is less calculated than compulsive: he continues sentencing others by standards he is actively violating himself.