Set in Edinburgh during the 1930s, an eccentric and passionate teacher at an all-girls secondary school has a unique teaching style, pushing her students to embrace art, culture, and independence instead of focusing solely on standard academic subjects. She takes special interest in a select group of girls whom she dubs as her "crème de la crème," encouraging them to think for themselves and exposing them to her own political and romantic ideals. Her unconventional methods and personal entanglements begin to attract scrutiny from the school’s conservative administration.

Her influence over the girls grows, causing tensions among them and stirring conflicts with fellow teachers. A complex relationship develops with one of her students, Sandy, who starts to see through her façade and becomes increasingly aware of the consequences of her mentor’s manipulations. The school authorities grow concerned about the teacher's dominance over her students’ lives, especially given the growing political unrest in Europe. Over time, loyalties are tested, and a series of revelations push the characters towards a dramatic confrontation, forcing decisions that will impact all their futures profoundly.