Before the play begins . . .
Agamemnon, king of Argos, becomes the general of the Greek expedition against Troy, and he sacrifices his daughter Iphigeneia in order for the ships to sail. Klytemnestra, his wife, is none too pleased at this development, and when Agamemnon returns from Troy ten years later, she kills him. In his absence, Klytemnestra has also taken up with Agamemnon’s cousin Aegisthus, who did not go to Troy.
Klytemnestra and Agamemnon have three other children: daughters Elektra and Chrysothemis, who have been in the court at Argos since before their father left; and son Orestes, who has been raised by his Tutor in the house of Strophios, where he becomes friends with his host’s son Pylades.
In the play today. . .
Orestes, now grown, returns to Argos with Pylades and at the urging of the Tutor, and we hear about their plan to arrive in disguise and to gain entrance to the palace by announcing that Orestes is dead. Although they hear Elektra grieving, they go immediately to leave offerings at the tomb of Agamemnon.
Elektra emerges, singing of her unhappiness living with the murderers of her father, and a Chorus of Argive Women try to console her. In their ensuing conversation, we learn that Klytemnestra blames Elektra for the threat that the absent Orestes poses, and that Aegisthus is not at home. When Chrysothemis joins the discussion, we find out that Chrysothemis does not share Elektra’s long misery, and that Klytemnestra and Aegisthus are ready to imprison the complaining Elektra. Chrysothemis, unable to convince Elektra to accept her situation, explains that she’s on her way to put offerings from Klytemnestra on Agamemnon’s tomb. It seems that Klytemnestra has had a disturbing dream that seems to foretell the the avenging return of Orestes. Elektra persuades her sister to substitute their own humble offerings–locks of hair and a belt–for the queen’s, and Chrysothemis leaves for the tomb.
The Chorus sing a song anticipating the return of Orestes, and then Klytemnestra comes out to confront her daughter. The Tutor, in disguise, interrupts them to announce and explain the supposed death of Orestes in a furious chariot race. Both mother and sister are upset by the news, to the surprise of the Tutor, who is invited into the palace.
Elektra and the Chorus are singing a song of grief for the dead Orestes when Chrysothemis comes running in with the news that Orestes must be home! Elektra protests that she must be wrong, since their brother is dead, and Chrysothemis explains that she has seen offerings that must be from Orestes, but Elektra does not believe her.* Hopeless, Elektra plans to take revenge herself, and Chrysothemis refuses to help her.
The Chorus sing the praises of brave Elektra, and Orestes and Pylades come on with the “ashes” of Orestes. When he sees the grief this brings to Elektra, Orestes realizes that he is speaking with his sister, and eventually he reveals himself to her and lets her join the plot.
Elektra breaks into song in her happiness, and almost gives the game away. The Tutor enters to say that the time is ripe, and the confederates go into the palace. After the Chorus sing about the fulfillment of a vengeful vision, Elektra comes out to stand guard, and we and she hear the violence within. Orestes announces the death, at his hands, of his mother, and they prepare a ruse for the returning Aegisthus: they show him Klytemnestra’s shrouded body and say it is Orestes’. When the confederates have Aegisthus in their power, they reveal the corpse of his dead wife, and then Elektra, Orestes, and Pylades take him into the palace for their final revenge.
*Note: This is a clear reference to The Libation Bearers, Aeschylus’ version of the same story.