Set in São Paulo during the mid-1980s, Agostinho (Paulo Betti) is an aging, weary physics teacher working at a night school for adult education. Married to Januária (Cláudia Mello), a retired school principal, his quiet and mundane life is upended when he falls passionately in love with one of his students, Márcia (Luiza Braga). Márcia is a much younger, emotionally unstable woman living with HIV and struggling with addiction. As Agostinho becomes consumed by his obsession with her, he willingly jeopardizes his marriage, career, and stability, spiraling into a self-destructive double life.