Bickerstaffe's libretto, based on Miguel de Cervantes' El celoso estremeño (a work translated into English as The Jealous Husband; the title literally means "the jealous Extremaduran"), consists of normal dialogue with a few interludes of song. It tells the story of an old miser who keeps his fiancée behind the closed door of their home for fear that she will not be faithful to him (in Cervantes's version, the woman is his wife). The opera's title comes from the large padlock that the old man keeps on the cottage door.