A Catholic school in the Bronx, 1964. The strong-minded principal Sister Aloysius - feared by students and colleagues alike - has her suspicions that one of her teaching fathers, a charismatic priest, is abusing a vulnerable pupil. Without proof, she is forced to take matters into her own hands. As the elements of her investigation come invigoratingly together like clockwork, this gripping story poses fascinatingly nuanced questions of moral certainty. Sister Aloysius is forced to wrestle with what's fact, what's fiction and just how far she'll go to expose what she sees as the truth.