A woman disguises herself as a man to infiltrate a prison and rescue her husband from political execution. Leonore assumes the identity of Fidelio to gain employment at the prison where her husband, Florestan, is held captive by the corrupt governor Pizarro. She must navigate the dangers of the prison environment, manage the affections of the jailer's daughter, and secure access to the deepest dungeons before the execution order is carried out. The narrative is presented as a libretto, utilizing dialogue and song to advance the plot within the rigid constraints of a stage production.

Discussion often centers on the dramatic tension inherent in the rescue plot and the moral fortitude displayed by the protagonist. Readers frequently highlight the effectiveness of the libretto in balancing personal sacrifice with broader political commentary on tyranny. Critics often note the structural efficiency required for a stage work, where every scene must propel the narrative toward the final act. The work remains a significant example of the rescue opera genre, with many focusing on the interplay between the characters' internal motivations and the external pressures of their environment.