ACT I. Spain, eighteenth century. In a prison, Marzelline, daughter of the jailer, Rocco, rejects the attentions of her father's assistant, Jacquino, who hopes to marry her. Her heart is set instead on the new errand boy, Fidelio. The latter, a hardworking lad, arrives with provisions and dispatches and is distressed by Marzelline's interest in him, especially since it has the blessing of Rocco. Fidelio is in fact Leonore, a noblewoman of Seville who has come to the jail disguised as a boy to find her husband, Florestan, a political prisoner languishing somewhere in chains. When Rocco mentions a man lying near death in the vaults below, Leonore, suspecting it might be Florestan, begs Rocco to ; ha take her on his rounds. He agrees, though the governor of the prison, Don Pizarro, allows only Rocco in the lower levels of the dungeon.
As soldiers assemble in the courtyard, Pizarro learns from the dispatches brought to him that Don Fernando, minister of state, is on his way to inspect the fortress. At this news the governor resolves to kill Florestan, his enemy, without delay and orders Rocco to dig a grave for the victim in the dungeon. Leonore, overhearing his plan, realizes Pizarro's evil nature and the plight of his victim. After praying for strength to save her husband and keep up hope, she again begs Rocco to let her accompany him to the condemned man's cell - and also to allow the other prisoners a few moments of air in the courtyard. The gasping men relish their glimpse of freedom but are ordered back by Pizarro, who hurries Rocco off to dig Florestan's grave. With apprehension, Leonore follows him into the dungeon.
ACT II. In one of the lowest cells of the prison, Florestan dreams he sees Leonore arrive to free him. But his vision turns to despair, and he sinks down exhausted. Rocco and Leonore arrive and begin digging the grave. Florestan awakens, not recognizing his wife, and Leonore almost loses her composure at the familiar sound of his voice. Florestan moves the jailer to offer him a drink, and Leonore gives him a bit of bread, urging him not to lose faith. Rocco then blows on his whistle to signal Pizarro that all is ready. The governor advances with dagger drawn to strike, but Leonore stops him with a pistol. At this moment a trumpet sounds from the battlements: Don Fernando has arrived. Rocco leads Pizarro out to meet him as Leonore and Florestan rejoice in each other's arms.
In the prison courtyard, Don Fernando proclaims justice for all. He is amazed when Rocco brings his friend Florestan before him and relates the details of Leonore's heroism. Pizarro is arrested, and Leonore herself removes Florestan's chains. The other prisoners too are freed, and the crowd hails Leonore.
-- courtesy of Opera News