Every month, during the full moon, a Brazilian fishing village receives a mysterious guest. A dolphin becomes a human man (Carlos Alberto Riccelli) known as "o boto" or dolphin man. He roams the village, engaging in trysts with various women. One of these women, Tereza (Cássia Kiss), is pregnant after their encounter, and she carries and gives birth to a dolphin child. Meanwhile, the men in the village are increasingly frustrated with the dolphin man because he frightens away fish.