This paper is the result of the comparativist analisys of the dialogical relations between the novel Dom Casmurro (1899), by Machado de Assis, and its cinematographic adaptation Capitu (1968), directed by Paulo Cezar Saraceni, also considering the screenplay written by Lygia Fagundes Telles e Paulo Emilio Salles Gomes. Therefore, the reflexions are based on the bibliographic research about the conceptual triad: intertextuality, intermidiality and adaptation. First, the concept of intertextuality is developed from the precepts listed by Tiphane Samoyault. Then, the phenomenon of the intermidiality is elucidated by means of postulates by Claus Clüver, Irina Rajewky and Lucia Santaella. The triad closes with the approach of the adaptation prac...