Monarchists and Republicans confront themselves in Araruna, a small town in the interior of São Paulo, in 1886, two years before the promulgation of the Golden Law. Sinhá Moça's love story, daughter of Colonel Ferreira, Baron de Araruna, and a slave-boy, with the young Dr. Rodolfo, an active Republican abolitionist, faced with the difficulties of the campaign for the abolition of slaves. The two meet on the train, when Sinhá Moça, after completing her studies in the provincial capital, returns to Araruna. Like Rodolfo, she has abolitionist ideas and criticizes her father's attitudes, fighting for the defense of blacks. Sinhá Moça, together with Rodolfo and other abolitionists, invade the slave quarters at night and liberate the blacks, giving them to the abolitionist associations, which guide them towards freedom.