O’Neill conceived of creating a modern psychological drama rooted in Greek legend in the spring of 1926, but Mourning Becomes Electra was not completed until the spring of 1931. Actually a trilogy of three full-length plays, it opened in October and was deemed a masterpiece by more than one critic. O’Neill said: “By the title Mourning Becomes Electra I sought to convey that mourning befits Electra; it becomes Electra to mourn; it is her fate; black is becoming to her and it is the color that becomes her destiny.”

The Greek source for O’Neill was the Oresteia of Aeschylus, from the fifth century b.c.e., the trilogy detailing the relationships of the house of Atreus. In the first play, after the siege of Troy, Clytemnestra murders her husband, the victorious Agamemnon; in the second, their son Orestes, with his sister Electra, murders his mother and her lover Aegisthus; in the third, Orestes is hounded by the Furies for matricide but is eventually freed from his guilt and acquitted of the crime. O’Neill reworked much of this story; he also drew upon the versions of Electra by Sophocles and Euripides, which focus upon the daughter, a haunted woman, torn by hate and love and never at peace.

The Mannon family (the name may be associated with “mammon” and the family’s materialism) is the center of O’Neill’s play, which is set in New England immediately after the Civil War. The house is described in the stage directions as resembling a white Greek temple, with six columns across the front porch. In the first play, The Homecoming, Christine Mannon (Clytemnestra) has taken a lover, Adam Brant (Aegisthus), while her husband, Ezra (Agamemnon), has been fighting in the war. Daughter Lavinia (Electra) is jealously aware of the affair and threatens her mother with exposure. In this section, mother and daughter are rivals for the love of Ezra and Adam.

When Ezra returns, Lavinia desperately tries to win his love and attention from her mother, as Ezra makes an impassioned effort to communicate with Christine, begging her to love him. Thinking only of her lover, she rejects him, and when he has a heart attack, she administers poison rather than medicine. In his death throes, he reveals Christine’s crime to Lavinia.

The triangular structure of the second play, The Hunted, includes Lavinia, Christine, and the newly returned battle-scarred Orin (Orestes). Each woman is seductive and persuasive with him, but Lavinia is victorious in convincing him that Christine killed Ezra and that he should avenge their father’s murder by killing Adam Brant. He accomplishes the act, which drives Christine to commit suicide and leads to Orin’s mental deterioration through his burden of guilt. In the final play, The Haunted, both Lavinia and Orin struggle to transcend their past crimes, first through incestuous love of each other, then through relationships outside the family. When this is impossible, Orin commits suicide, and Lavinia secludes herself in the Mannon mansion.

Although the plot represents another reworking of the O’Neill family drama, with the author infusing autobiography into both Lavinia and Orin, it is also faithful to the Greek legend. In addition, O’Neill borrowed other elements from the Greeks. He adopted the form of the trilogy, and he created the character of Seth to function as the leader of the chorus. The townspeople act as that chorus. Most important, O’Neill sought to find an equivalent to the Greek sense of fate, the inescapable destiny toward which the characters rush, which the Greeks achieved through their culture’s belief in gods and goddesses and in their shared morality.

Such a climate was difficult to approximate in a modern culture that does not believe in such external forces. To solve the problem, O’Neill set the play in a Puritan-derived New England culture, similar to that of Desire Under the Elms, a culture which insisted upon personal responsibility and which offered no easy absolution or forgiveness. The sense of fate surrounds the past, present, and future of the family, as the past sins of the father (and mother) are redressed by the children with greater sins, for which they in turn must suffer in the future. “I’m the last Mannon,” says Lavinia as she imprisons herself in the mansion. “I’ve got to punish myself.” The tragic destiny of the Mannon family is oblivion.

The sense of fate is further reinforced by the use of the mask concept. O’Neill, still fascinated by the device, wrote one draft of the play with characters donning and removing masks, as in The Great God Brown; he soon rejected the device, although not its significance. Instead, he enlisted the actors’ skills to create expressions on the faces of the Mannon family like “life-like masks.” These emphasize the family similarity and the ties of blood that bind them together. In the final section, both Lavinia and Orin are altered in appearance and resemble their parents even more closely, a reminder that despite all resistance, heredity is destiny.

This view corresponds to that of the Darwinian naturalists, who describe humanity as the product of heredity and environment; thus, human beings are victims of forces beyond their control. Indeed, the play has links with the naturalistic theater. Where the naturalists claim that because of these forces people are not responsible for their actions, however, the Puritan mind claims that people should suffer guilt and be punished. Perhaps it is significant that in the Greek play Orestes is forgiven by the Eumenides and Electra is married to Pylades, a prince of Phocis, but in O’Neill’s puritanical play there is no such mercy.

Once again, in Mourning Becomes Electra there is no moral message, only intense experience. The family is depicted in a tortured web of dependencies, jealousies, hatreds, and loves, which O’Neill describes without judgment. Reading the play later, he declared himself satisfied with its “strange quality of unreal reality.” Finally, if Mourning Becomes Electra is not the artistic equivalent of the Oresteia, it is the closest example that twenty-five hundred years of theater have produced.