Raised by a vehemently non-religious, single mother (Nicholson) in rural Tennessee during the '50s, a scholarship to Catholic school soon finds Cathleen (Qualley) drawn into all the mystery and romanticism of a life devoted to the worship and servitude of God. With the dawn of the Vatican II era, radical changes in the Church are threatening the course of nuns' lives. Cathleen finds herself struggling with issues of faith, sexuality, and the changing administration.