ACT I: The courtyard of the prison
Jaquino is watching Marzelline iron. When he tries to strike up a conversation, she puts him off. Marzelline sympathizes with Jaquino but can think only of her love for Fidelio. They are interrupted by a knock at the door. When Jaquino returns to continue his suit she answers with a firm 'No!'.
Left alone, Marzelline dreams of her future happiness with Fidelio (O wär´ ich schön mit dir vereint — Oh, if I were already one with you). Rocco enters, looking for Fidelio (really Leonore in disguise), just as he returns, struggling with heavy, newly repaired chains, from a trip to the blacksmith. He also brings dispatches for Pizarro. Rocco praises him for his diligence and promises that his assistant will soon be rewarded, hinting he may marry Marzelline.
In a quartet, the characters sing of their feelings (Mir ist so wunderbar — It is so wonderful to me). Marzelline thinks of her future happiness, Leonore is apprehensive of the danger she is in, Jaquino is jealous and Rocco thinks of the happiness of the young couple. Rocco announces that Fidelio and Marzelline can be married as soon as Pizarro leaves for Seville, then sings of the happiness money brings (Hat man nicht auch Gold — If one doesn't also have money). Fidelio tells him married love is better than gold. She begs to be allowed to help him in caring for the prisoners in the dungeons. Although he has had orders that no one else is to go to the cells, he admits he needs help. He agrees to let her accompany him to all but one very secret dungeon. There is a prisoner there that cannot last much longer. Leonore guesses he must be her husband. Marzelline begs Fidelio not to go to the dungeons, but he states his determination to go.
A march hails Pizarro's arrival. He is handed his dispatches warning him that the government is sending Don Fernando to investigate stories of abuse at the prison. (Fernando is a friend of Florestan's but believes him dead.) Pizarro decides Florestan must die at once (Ha! Welch ein Augenblick! — Ha! What a moment!). He orders that trumpeters be posted to warn him of Fernando's arrival, then flatters Rocco and offers him money to kill the special prisoner. When Rocco demurs, Pizarro decides to do the act himself and orders the jailer to dig a grave in a ruined cistern for the corpse. Leonore has overheard and resolves to save the prisoner (Abscheulicher! — Abominable one!).
Jaquino is still pursuing Marzelline, but Rocco tells him she will marry Fidelio. In turn, Leonore and Marzelline beg Rocco to allow the prisoners to come up into the courtyard for some fresh air. He agrees but only for the prisoners in the upper cells.
As Leonore searches the face of each emerging prisoner, hoping to find her husband, the prisoners rejoice in the sunlight (O welche Lust — Oh what joy). Rocco has asked Pizarro's permission for Marzelline and Fidelio to marry, and it has been granted. The jailer will also be allowed to take his helper with him into the dungeons where they must dig a grave. At her anxious question, he admits the man is not yet dead; Pizarro is to kill him. She asks if they could not set him free, but Rocco says that is impossible.
Pizarro enters, raging that the prisoners have been let out. Rocco explains it was to celebrate the king's name-day. Pizarro orders them back to their cells and they sadly bid farewell to the sun (Leb´ wohl — Farewell). As they leave, Rocco and Leonore start their descent to the dungeon.
ACT II, Scene 1: Florestan's dungeon
Alone in the darkness, a chained Florestan despairs (Gott! Welch Dunkel hier! — God, What darkness here!). He does not complain, as he has done his duty by speaking up, though it has led to his imprisonment. In his delirium, he sees a vision of Leonore leading him to Heaven, then sinks down as Rocco and Leonore descend into the cell. Leonore tries unsuccessfully to see the prisoner's face. As she and Rocco start to dig in anticipation of Pizarro's arrival, Leonore resolves to save the prisoner, whoever he is.
When Florestan wakes and demands the name of the prison's governor, Leonore recognizes him. When he is told Pizarro's name, he begs Rocco to send a message to a certain Leonore Florestanin Seville, saying her husband is lying in chains. Rocco responds that is impossible but, when asked for some water, tells his helper to give the prisoner some wine. As Florestan thanks Fidelio, she manages him to give him a little bread. The prisoner realizes that 'the 'boy' and Rocco are moved by his plight. As Rocco whistles to signal Pizarro, Florestan wonder if he will ever see Leonore again.
Pizarro arrives, disguising his voice as he orders 'the boy' to leave. Instead she hides. Gloatingly, Pizarro reveals himself to Florestan and draws a dagger to stab him. Leonore throws herself between them announcing: "First you must stab this breast". When Pizarro pushes her away, she draws a pistol: "First kill his wife!" At this dramatic moment, a trumpet announces the arrival of Don Fernando.
As Pizarro and Rocco stand dumbfounded, Florestan and Leonore embrace, and Jaquino and some soldiers enter to announce the arrival of the minister. Pizarro curses, and Rocco, glad to be free of the oppressor, wonders about his own fate. Leonore and Florestan sing of their joy (O namenlose Freude! — Oh nameless joy!).
ACT II, Scene 2: The castle courtyard
The castle guards march in, followed by Don Fernando and Pizarro. Jaquino and Marzelline lead in the prisoners, and Don Fernando, on orders of the king, frees them all. Rocco brings in Florestan and Leonore, asking mercy for them also. As a stunned Don Fernando recognizes his old friend whom he had thought dead, Rocco tells how Leonore has come to the prison disguised as a boy. The villain Pizarro is led away, the crowd calls for his punishment, and Don Fernando gives Leonore the privilege of removing Florestan's chains. All join in a paean to married love (Wer ein solches Weib errungen — He who has won such a wife).
Courtesy of San Diego Opera's Operapaedia