Fifteen-year-old Sabine is unusually confident and analytical. She is also extraordinarily gifted in mathematics. This tender romance chronicles her coming-of-age at the hands of a gentle and fun-loving 40-year-old Czech playwright named Jiri. Because she is so bright, Sabine, who lives in a low-income housing project with her unemployed parents and little sister, makes money on the side doing other people's homework. One day Jiri sees her taking money from some thankful young men on a bus and mistakes her for a prostitute. Under this impression, he invites her to his hotel and with her acquiescence gently becomes her first lover. Sabine approached the situation with logic and afterwards remains cool and calculating until she later spies Jiri with another woman. When faced with that, Sabine's cool demeanor disintegrates and trouble follows.