In frigid 1960s Boston, Eileen shuffles between her father’s dingy, emotionally haunted home and the prison where she works alongside colleagues who have ostracised her. When an intoxicating woman joins the prison staff, Eileen is taken. Just when the possibility of a salvational friendship (or maybe more) takes hold and forms a singular glimmer in Eileen’s darkness, her newfound confidant entangles her in a shocking crime that alters everything.