The opera is in two acts and 14 scenes. The setting is the Cenci Palace, Rome, in the late 16th century.
Count Francesco Cenci has arranged for a masked ball to celebrate the death of his two sons at Salamanca. The people despise the Count, and his daughter Beatrix and his second wife Lucrecia live in fear of him. Beatrix wants to escape by having her former suitor, Orsino, communicate a letter to the Pope. Orsino, who has taken Holy Orders, destroys the letter.
At the ball, the guests are repelled at the idea of the Count celebrating the deaths of his own sons. They leave, to the terror of Beatrix, who does not want to be alone in her father's company. Orsino enters and covers his destruction of Beatrix's letter by saying that the Pope has rejected her plea. Left alone, the Count rapes Beatrix.
When in exile after reporting her father's act, Beatrix's older brother Giacomo convinces Beatrix to kill her father. She then hires two assassins for the task, Olimpio and Marzio. Lucrecia gives Cenci a sleeping potion. The assassins kill the Count and conceal his body.
Months later, Orsino announces that the Count's body has been discovered. One of the assassins has been killed, and the other has confessed to the murder. Beatrix is arrested for the crime, and then bound and tortured. Finally, she is executed at the scaffold.
