The title character, Florencia Grimaldi, is a famous opera soprano returning to her homeland to sing at the opera house in Manaus with the hope that her performance will attract her lover Cristóbal, a butterfly hunter who has disappeared into the jungle. She boards the steamboatEl Dorado for a trip down the Amazon River, along with several passengers who are traveling to hear her sing. The passengers, however, are unaware of her identity. One of them, Rosalba, is a journalist planning to write a book about Grimaldi and hoping to interview her. In preparation, Rosalba has compiled a notebook for two years with information about the diva. Florencia spends her time on the boat brooding about Cristóbal. She does not interact much with the other passengers initially, and the thread connecting the subplots in the story is provided by the ship's mate, Ríolobo, who also is the focus for the elements of magical realism. Ríolobo functions as a narrator, one of the characters, and the intermediary between reality and the mystical world of the river. Meanwhile, Rosalba is beginning to fall in love with the steamboat captain's nephew, Arcadio, who rescues her notebook when it falls overboard. The two play a game of cards with Paula and Álvaro, a bickering couple who are also looking forward to Grimaldi's performance. After the game, a storm develops and Álvaro saves the boat but is thrown overboard. With the captain tragically obliterated and Ríolobo having disappeared, Arcadio takes the helm but the ship runs aground. Ríolobo reappears in the form of a river spirit and the storm stops after he calls upon the river gods.
Act 2
The characters recover from the storm. Florencia seems to feel Cristóbal's presence and is unsure whether she is alive or dead. Rosalba, focused on her objective, resists the attraction she and Arcadio feel for each other. Meanwhile, Paula, in spite of their constant fighting, recognizes that she still loves Álvaro and mourns his loss. Again Ríolobo appeals to the river and Álvaro is suddenly returned to the ship. In the storm, Rosalba's precious notebook has been lost again, and when it is recovered again it has been ruined by the water. Distraught, Rosalba argues with Florencia about the meaning and value of its contents when suddenly she discovers that the woman she has been arguing with is the very singer she has been longing to interview. Realizing how Florencia draws inspiration from love, Rosalba decides to give in to her feelings for Arcadio. The boat arrives in Manaus, but a cholera outbreak keeps the passengers quarantined aboard the ship. Florencia despairs of a reunion with Cristóbal, but in the end she is magically transformed into a butterfly, to represent her spirit going off to be reunited with her lover.