Don Fernando arrives at the end to free the character Florestan from prison upon learning that it is Leonore dressed as the title character.  
Important arias in this opera include Hat man nicht auch Gold beineben and Gott! welch Dunkel hier!  In a side plot, Jacquino is rejected by Marzelline, who loves the title character.  Marzelline's father, Rocco, is the jailer and the only one allowed in the lower dungeon levels according to Don Pizarro.  Don Fernando arrives at the end to free the character Florestan from prison upon learning that it is Leonore dressed as the title character.  FTP, identify this only opera by Beethoven.
Important arias in this opera include Hat man nicht auch Gold beineben and Gott!
Fidelio