What is the main conflict in Mourning Becomes Electra by Eugene O'Neill?

Like Oresteia, O'Neill's play features themes of fate, revenge, hubris, adultery, and honor. Many critics note that the play reflects his recurring concerns about the unsuccessful struggle of an individual to escape a tragic fate and the dark nature of human existence. The play is structured as a trilogy, with three different plays The Homecoming, The Hunted, The Haunted comprising the story.