Anna, in her mid-thirties, independent and professionally successful, has just been left by her lover. She books a trip to Borneo to forget Roger in the heat of the jungle. In fact, a trip into the rainforest distracts her – a mysterious twitch and an unfamiliar sensation in her left leg capture all her attention. Back in Sweden, Anna has her "travel souvenir" examined by tropical specialist Willof. He is thrilled: a rare species of butterfly has chosen Anna as its host. Willof persuades the chosen one to move into his butterfly house and carry the larvae in her leg until they hatch. She settles into the greenhouse, where her memories of the past soon intertwine with the present. And the supposed oasis? It quickly turns into a place of strange occurrences.