Carla Nowak, a dedicated sports and maths teacher, takes up her first post at a upper secondary school. Her idealism makes her stand out among her new colleagues. When a series of thefts occur at the school and one of her pupils is suspected, she decides to get to the bottom of the matter on her own. Carla tries to mediate between outraged parents, bossy colleagues and feisty pupils, but is ruthlessly confronted with the structures of the school system. The more desperately she tries to do everything right, the more the young teacher threatens to break.