It's 1964, St. Nicholas in the Bronx. A charismatic priest, Father Flynn, is trying to upend the schools' strict customs, which have long been fiercely guarded by Sister Aloysius Beauvier, the iron-gloved Principal who believes in the power of fear and discipline. The winds of political change are sweeping through the community, and indeed, the school has just accepted its first black student, Donald Miller. But when Sister James, a hopeful innocent, shares with Sister Aloysius her guilt-inducing suspicion that Father Flynn is paying too much personal attention to Donald, Sister Aloysius sets off on a personal crusade to unearth the truth and to expunge Flynn from the school. Now, without a shard of proof besides her moral certainty, Sister Aloysius locks into a battle of wills with Father Flynn which threatens to tear apart the community with irrevocable consequence.