Orestes and Electra are sleeping inside Apollo's shrine, where the statue of Apollo protects them. The Furies surround them, jesting among each other about the various tortures they will inflict on the siblings as soon as they leave the god's protection. The Furies sing and buzz, waking Electra. She sees Orestes and recoils from him, haunted by the memory of the murders of the night before. Orestes sees that her eyes have turned dead and her face appears ravaged so that she looks like Clytemnestra. Electra asserts that the murders were not her fault, insisting that she only dreamed about it, but it was Orestes who actually carried it out. Orestes attempts to convince her that they must assume responsibility for the murders together, but Electra cannot find the strength to do so and the Furies goad her into reliving the murders and seeing Orestes as a frightening murderer.
Orestes attempts to keep Electra from listening to the Furies, but she cannot help it. The Furies convince her that she deserves to be punished, and she surrenders herself to them. At this moment Jupiter enters. He attempts to convince Orestes that he is a criminal and that he must atone, but Orestes retorts that he will not atone for something he does not consider a crime. Jupiter then turns to Electra, telling her that he has come to save them. He tells her that she was not responsible for the crime; she had only fantasized about it like a child. She needs only repent and Jupiter will gladly forgive and give the throne to the siblings. Orestes refuses the throne, saying that he will not take the place of the man he has killed. Orestes sees himself as the savior of the city, but Jupiter mocks him, saying that the Argives hate their "savior" and are waiting outside to kill him; he is completely alone.
Orestes still refuses to repudiate his actions. In response, Jupiter draws apart the walls of the temple and speaks with a booming voice. He tells Orestes of how he himself has ordered the universe and nature based on Goodness, and by rejecting this Goodness Orestes has rejected the universe itself. Orestes stands alone against nature. Orestes replies that he accepts his exile from nature and from the rest of humanity. He has realized his freedom and can no longer return to nature and Jupiter's Good. Orestes argues that Jupiter is the king of nature, but not of humanity. He made the mistake of making human beings free and thereby lost his power over them. Orestes announces his intention to free the Argives from their remorse. Jupiter says that it was prophesied that a man would come signaling his downfall and Orestes appears to be that man. Orestes and Jupiter agree to part ways, each feeling sorry for the other. As Jupiter leaves, Electra follows him. Despite Orestes's entreaties, Electra believes that he can bring her nothing good. Instead, she chases after Jupiter and promises him her repentance. The Furies leave her alone, waiting for Orestes to weaken so they can attack him. The Tutor enters but the Furies will not let him through. Orestes orders him to open the door so that he may address his people.
Orestes stands up and tells the Argives who he is. He informs them that he has taken their crimes upon himself and that they must learn to build a new life for themselves without remorse. He says that he wishes to be a king without a kingdom, and promises to leave, taking their sins, their dead, and their flies with him. Telling the story of a piper who drew the rats of Scyros away with him, Orestes walks off into the light as the Furies chase after him.
Acts I and III, structurally located around the axis of Orestes's choice to act in Act II, can usefully be contrasted with each other. Act I began with an atmosphere that was suffocating and offensive to all the senses as Orestes first entered Argos. In Act III, this veil of repression is lifted by Orestes's moral force. Although he wakes up hiding in a shrine with the Furies surrounding him, Orestes has clearly managed to hold on to his freedom. He challenges Jupiter directly and fends him off, replacing the repentance of Act I with liberation. Acts I and III also show Orestes and Electra superficially exchanging their roles. In Act I Electra is dreaming of bloody vengeance while Orestes remains detached. By Act III Electra has repudiated the vengeance and it is Orestes who takes it upon himself. Electra serves as Orestes's foil throughout the play. She grounds the play in the ancient Greek notions of destiny and vengeance, though at the end she realizes that these ideas are too heavy for her. Orestes, on the other hand, is clearly chronologically out of place in ancient Greece with his modern notions of freedom and human justice.
Having woken up, Electra realizes that her dream has become a nightmare. In the past she dreamt with joy of Clytemnestra and Aegistheus lying in a pool of their own blood. Now she has dreamt the same dream, but is has brought her intense horror. From the very beginning of Act III Electra says that she is being ravaged by Orestes's crime, not her own. She attempts to separate herself from the crime, but she isn't certain how. Jupiter offers her a solution: she did not freely choose the murders but only fantasized about them. Convinced that Jupiter is right, Electra gladly surrenders to him. Unlike Orestes, Electra has not felt freedom "crashing down" on her. She feels only guilt and horror at her complicity in matricide. Jupiter offers to save her from the Furies and give her the throne provided she repents. Unwilling to face a life where all eyes judge her as a killer, Electra gladly accepts Jupiter's offer, vowing to be his slave. She thus takes her mother's place. Clytemnestra's earlier prediction that Electra's life will be ruined in a single day comes true.