After 25 years of marriage, Reiko notices her husband paying unusual attention to his appearance and going out more often. She secretly follows him and is shocked to see him meet one of her friends. Continuing the pursuit, she runs into Nakata, the friend’s husband, who has also been following them. They trail the cheating pair to a hotel and take the room next door. As they listen through the wall, humiliation, anger, and lust overwhelm them. Deciding they may as well do the same, the two betrayed spouses give in and have sex themselves.