Three married women in their thirties are former college classmates. Though their daily lives are comfortable, they feel unsatisfied with sex with their husbands. On a hot spring getaway, they coincidentally reunite with an ex-boyfriend from university days. In the mixed open-air bath, they end up pressing their naked bodies together. As the three wives seek infidelity, their husbands—also searching for excitement during the trip—join in, rapidly escalating desire. That night at the inn, each becomes consumed by adulterous sex, eventually spiraling into a massive seven-person orgy.