In this adaptation of the work by Machado de Assis, Bentinho promises his mother he will become a priest but follows a different path: he marries Capitu. Years later, a doubt consumes him—did she cheat on him with Escobar?
Bentinho receives the nickname "Dom Casmurro." Dona Glória is warned that Capitu might interfere with her plans for Bentinho. Bentinho calls José Dias for a talk.
Bentinho makes a pact with José Dias. Capitu's eyes draw attention. Bentinho and Capitu kiss. Capitu makes a vow to Bentinho. Bentinho leaves for the seminary.
Bentinho meets Escobar. Bentinho receives news about Capitu. Dona Glória falls ill. Capitu sees Escobar. Bentinho becomes jealous of Capitu and makes a decision regarding the seminary.
Bentinho and Escobar share secrets. A friend of Bentinho's passes away. Years go by; Escobar marries Sancha, and Bentinho completes his studies and marries Capitu.
Bentinho grows suspicious of Capitu. Ezequiel is born. Escobar meets a tragic end. Bentinho shows revulsion toward his son. Bentinho accuses Capitu of betrayal.