In Anouilh's adaptation of Antigone, the relationship between Antigone and her sister Ismene serves as a vital exploration of conflict and allegiance. Antigone's determination to honor her brother by defying the king's decree starkly contrasts with Ismene's adherence to state laws. This clash reflects broader themes of duty, loyalty, and personal conviction. Analyze how their relationship evolves in the play and its implications on the overall narrative.