Two college couples, Pierre and Sophie, and Frank and Maddison, who seek a relaxing retreat at an Airbnb in rural Cornwall, Connecticut. Their host, Jonah, possesses an unsettling demeanor and provides a curious warning about a locked basement. What begins as a pleasant escape quickly devolves into a struggle for survival as the group confronts an insidious force stemming from the forbidden basement and a broken mirror. As the possessed girls turn on their friends, the couples are drawn into a terrifying ordeal that culminates in the shocking revelation of Jonah's involvement in a continuing, dark ritual.