Three people live together: a couple and their wife and his wife's brother. The wife has been having physical relations not only with her husband but also with his brother with his approval. The film closely follows the unusual daily routine of the couple having sex at night, and then having sex with the sister and brother after the husband leaves for work. The three of them know that they are having sex separately, but they have an unspoken rule that they do not watch each other. With the consent of each of them, they show their sex in front of their husbands...
