In Beethoven's only opera, "Fidelio", who is the heroine Leonore's love-interest?

In "Fidelio", the only opera composed by Ludwig van Beethoven (1770-1827), the heroine, Leonore, is in love with Florestan, who has been imprisoned in a dungeon in Seville as a result of trying to expose the crimes of the dastardly Don Pizarro. Pizarro has also spread false rumours concerning Florestan's death.

Leonore has disguised herself as a prison guard, adopting the name "Fidelio" (meaning "The Faithful One") to gain access to her beloved. Matters are further complicated by the fact that Marzelline, the daughter of another, more humane prison official named Rocco, has fallen in love with Fidelio, not realising that (s)he is, in fact, a woman.

The opera contains much beautiful and memorable music, including the first act quartet, "Mir ist so wunderbar" ("A wondrous feeling fills me), the prisoners' chorus, and Florestan's haunting prison aria, "Gott, welch dunkel hier" ("God, it is so dark here") in which he is granted a vision of Leonore coming to his rescue.

The vision is turned into reality, and the opera ends happily (apart from for Pizarro) with the crowd singing a song in praise of Leonore, with a tune that may well be familiar from the Ode to Joy concluding Beethoven's 9th symphony.

People may be interested to know that although the libretto was finally written by Joseph Sonnleithner, Beethoven initially considered cooperation with Emmanuel Schikaneder, more famous for writing the libretto to Mozart's "The Magic Flute".