An exhausted Electra bewails her fate as an outcast before her own house, guardian of Orestes who is maddened by the Furies. The city will today vote on their lives. But Menelaus has just arrived from the war, offering hope of reinstatement or at least rescue.
A rather empty-headed Helen (her first comment to the distressed Electra is her sadness that she is unmarried!) asks Electra to make a sacrifice for her to Clytemnestra. Electra is indignant, but suggests Hermione as an alternative. Hermione departs for the tomb.
The Chorus of Argive women enter and Orestes awakens, in a frenzy; then the fit passes. Menelaus enters, and considers Orestes' plea for help. Tyndareus arrives, disgusted at the sight of Orestes: that Clytemnestra was wrong does not matter, for murder must be met with law and banishment if the cycle of revenge is to be stopped. Orestes' defense is a confused jumble of arguments used in the Oresteia (my father was the true agent of my birth, my mother corrupted his bed, all wives will kill their husbands if I am punished). Tyndareus vows emnity if Menelaus aids Orestes. Menelaus declines military assistance, but will speak for him in the assembly.
Pylades enters, banished from Phocia for his part in the murder. The will go to the assembly and Orestes will argue his case before the people.
A messenger announces to Electra the scene at the assembly: Menelaus did not speak; Orestes was only able to convince the people not to stone them but to allow suicide. Orestes and Electra discuss how to kill themselves.
Pylades suggests that they kill Helen and take Hermione hostage. Orestes and Pylades enter the palace. Meanwhile, Electra and the chorus lay in wait for Hermione, and when she returns from the tomb, they hand her over to Orestes and Pylades. A Phrygian servant announces (in broken Greek) the scene: O. and P. pretended to supplicate Helen to intervene for them with Menelaus; then once she was alone they tried to murder her, but she was apotheosized.
Menelaus arrives in rage and fear. Orestes and Pylades appear on the roof with swords threatening Hermione, while Electra waves a torch and threatens to burn down the house. Apollo appears, ex machina, and announces the apotheosis of Helen; that Menelaus must calm himself and marry again; that Orestes must seek justice in Athens and then marry Hermione (!); that Electra and Pylades must marry. He will reconcile Argos to Orestes. Orestes rejoices and releases Hermione. Menelaus happily betroths his daughter to her erstwhile murderer. At peace, they depart.