The film, based on the novel by Anna Maria Ortese, narrates the adventures of a rich, dreamy Italian Count, Aleardo, who, while traveling on a sail boat ends up on the remote island of Ocana, off the Portuguese coast. Here, three impoverished Portuguese aristocrats live in dire poverty, cut off from the world and thrown back to the nineteenth century. He finds the melancholy, tormented Ilario and his sinister half-brothers Hipolito and Felipe together with a female servant they treat like an animal they mysteriously call "Iguana". Fascinated by the extravagance of his hosts and troubled by the suffering and charm of the young "Iguana", Aleardo stays on the island for a night and a day. During which he is drawn into an intrigue with disturbing implications. Is the Iguana the latest transformation of the devil or is she merely a victim, an innocent creature to be saved and protected at any cost? Aleardo's journey becomes an hallucinating descent to hell. The Iguana can be read as a metaphor. "The horizon showed only a flush of amber light, yet there was still a leeward glimpse of the low, naked coast of Portugal until, shadow-like, it finally disappeared".