Answer
Bluebeard's Castle is the sole opera by Hungarian composer Béla Bartók. It is a one-act opera based on the Hungarian folktale of the same name. The opera tells the story of Bluebeard, a wealthy and mysterious man who invites Judith, a young woman, to his castle. Judith is curious about the castle's seven locked doors, and Bluebeard eventually agrees to let her open them.