Isabella is trapped. She cannot accuse him openly since his reputation would back up his denial. She has no choice but to go to her brother with the story so that he may prepare himself for his execution.
It is important in interpreting Isabella's refusal of Angelo's offer to note her reason for it: "Better it were a brother died at once, / Than that a sister, by redeeming him, / Should die for ever" (106-108). The reader should remember that Isabella, deeply religious, is on the verge of entering the convent. To her, life is a mere prelude to eternity. In considering Claudio's demands, she is not weighing her brother's life against her virginity, but Claudio's life on earth against the everlasting life of her immortal soul. Further, to submit to Angelo's demands would constitute a sin against God, to whom she is ready to devote her life. Her decision may seem a harsh one from Claudio's standpoint, but by her stern religious values it is logical and right. Isabella firmly believes that her brother will agree with her estimation of the situation.
