In 1964 the winds of change are sweeping through Sister Aloysius’ St. Nicholas school. Father Flynn, a charismatic priest, is advocating reform of the school’s strict customs, and the first black student has just been accepted.  When a fellow nun tells Sister Aloysius that Father Flynn may be paying too much personal attention to the student, Sister Aloysius begins a personal crusade against the priest — despite her lack of evidence.