It updates the Greek myth of Orestes to the family of a Northern general in the American Civil War. Agamemnon is now General Ezra Mannon, Clytemnestra is his second wife Christine, Orestes is his son Orin, and Electra is his daughter Lavinia. As an updated Greek tragedy, the play features murder, adultery, incestuous love and revenge, and even a group of townspeople who function as a kind of Greek chorus. Though fate alone guides characters' actions in Greek tragedies, O'Neill's characters have motivations grounded in 1930s-era psychological theory as well. The play can easily be read from a Freudian perspective, paying attention to various characters' Oedipus complexes and Electra complexes.
Mourning Becomes Electra is divided into three plays with themes corresponding to The Oresteia trilogy by Aeschylus. In order, the three plays are titled Homecoming, The Hunted, and The Haunted. However, these plays are never produced individually, but only as part of the larger trilogy. Each of these plays contain four to five acts, and so Mourning Becomes Electra is extraordinarily lengthy for a drama. In production, it is often cut down. Also, because of the large cast size, it is not performed as often as some of O'Neill's other major plays.
A notorious Oscar upset occurred in connection with the film. All who saw it had taken it for granted that Rosalind Russell would win for her performance as Lavinia, to the point that Russell actually began to rise from her seat just before the winner's name was called. However, it was Loretta Young, and not Ms. Russell, who was named Best Actress (for her performance in The Farmer's Daughter).
While forgotten in the US, it was shown on British TV in the early 1960s and given such good reviews that it was actually released in the movie theaters.