Lavinia enters the sitting room. To her horror, she finds herself wishing for Orin's suicide. She implores the portraits to show her Orin's salvation.
Seth appears in the doorway, complaining that the maid is complaining of ghosts against. Lavinia leaves to talk to her. The doorbell rings and Seth lets Hazel and Peter in and exits anew. Uneasy, Hazel complains that Lavinia cannot continue keeping Orin shut up since she is a bad influence. Orin must stay with them for a time.
Orin appears, glancing about to check for his sister. He insists on seeing Hazel alone. He goes to the study and returns with a large sealed envelope, enjoining her to keep it safe. She should only open it if something happens to him or if Lavinia tries to marry Peter. Lavinia can have no happiness and she must be punished.
Hazel implores Orin to confide in and come away with her. Orin furtively suggests that he sneak out. Hazel indignantly refuses to engage in such deceptions. Lavinia is heard from the hall, and Orin hastily sits on the couch.
Lavinia starts at seeing the pair alone. Forcing a joking tone, she notes that Hazel is hiding something. Orin comes to Hazel's rescue by informing her sister that he will be moving in with her for a time. Lavinia refuses and Hazel springs up in rage. She loves Orin better than her and he must move. She prepares to leave, trying to keep Orin's envelope hidden behind her back. Lavinia blocks the door, demanding that she relinquish the manuscript. Rushing to Orin, she beseeches him to make her surrender it—she will do anything. Orin complies and instructs Hazel to forget his "rotting ghost." Hazel hurries out.
Orin makes sure his sister understands she can never see Peter again. A "distorted look of desire" comes into his face. Lavinia does not understand how much she had meant to him since they killed Christine. Perhaps he loves her too much. Caressing her hair, he remarks that she seems neither his sister nor mother but some stranger with the same hair—Marie Brantôme perhaps? Lavinia stares at him in horror, saying, "For God's sake—! No! You're insane! You can't mean—!" Orin replies that otherwise he cannot be sure she would not leave. Without "certainty," he would go mad and confess.
In Mourning Becomes Electra you write: "Oedipus was the Theban king who unwittingly killed his father and MURDERED his mother." [Emphasis mine].
It should read: "Oedipus...MARRIED his mother!"
(Oedipus' mother Jocasta did commit suicide after learning her lover was her son. Oedipus however did NOT "murder" her.)