It is the throne-room of the palace. A soldier comments on the fact that the flies are "all crazy" tonight. Clytemnestra asks Aegistheus what's wrong with him, and he replies that the crowd would have gone out of control if he hadn't played on their fear. He is aware of his lies and is tired of it all: "The black of my robes has seeped through to my soul." He claims not to have remorse; he says that he is simply very sad; then he rejects the amorous advances of Clytemnestra, calling her a whore. It is the gaze of Agamemnon that he fears, and he has actually begun to believe the lies about the dead spirits. This shows the weakening force of Aegistheus: He is not the tyrant he makes himself out to be, and he is now a prime target for the actions of Orestes. He sees himself as an empty shell: "I see I am more dead than Agamemnon."
Zeus enters, and Aegistheus does not recognize him. Zeus flashes lightning, and Aegistheus realizes who he is. He tells Zeus that people are afraid of the god; the latter replies: "Excellent! I've no use for love." Zeus tells him that Electra and Orestes are going to kill him. Aegistheus reacts stoically: "That's in the natural order of things." Zeus then shows his true colors: He is after Orestes' blood and would not care if he rotted to death. Zeus orders Aegistheus to have Orestes captured; the tyrant king resists, but Zeus knows that he will obey: He always does. Aegistheus then has a moment of dispute with Zeus; he wants to know what gives Zeus the right to try and save Aegistheus' life; one suspects that Aegistheus would prefer to die, and indeed he affirms this. Zeus gloats over Aegistheus's crime of fifteen years ago; for the murder of one man, twenty thousand living people have spent fifteen years in anguish, and this is real pleasure for Zeus. Aegistheus struck Agamemnon dead in a moment of rage and frenzy, not having thought out his actions with clarity. That is why he looks back now, fatigued and disgusted with his fraud. Orestes, on the other hand, is thinking everything through very carefully and, as a result, will suffer no remorse, which is why Zeus wants to prevent the murder of Aegistheus: He wants to prolong Aegistheus's deep remorse as long as he can; when Aegistheus dies, so too does Zeus' investment in the massive remorse. Aegistheus talks about the order which he has preserved in his kingdom, knowing full well that the people are free, that they could set his palace in flames if they knew they were free. Zeus woos him, calling him a "mortal brother" and comparing himself to him. He convinces Aegistheus through emotional rhetoric to do his will, placing the responsibility for the deaths of Orestes and Electra on Aegistheus's shoulders. Sartre demonstrates that even gods can have "bad faith," shirking their responsibility.
Zeus departs as Electra and Orestes bolt into the room, barring the door before Aegistheus can call for help. Aegistheus is glad about their arrival: It is time to die, and he does not wish to resist. Death, for him, comes as a relief after fifteen years of hell on earth. Orestes strikes him down and feels no remorse: "Why should I feel remorse? I am only doing what is right." His goal is to free the people of Argos from Aegistheus' tyranny. Aegistheus rises weakly and curses them both, telling them to beware of the flies. He dies then. Orestes wants to kill the queen next, but Electra intervenes, claiming that Clytemnestra can no longer hurt anyone. This is Electra's first step backward into a life of subservience and fear. Orestes has come to free them from fear, yet Electra now clings to her former lifestyle. Orestes departs alone, having pointed out a change in Electra's behavior. She is the kind of person whom Sartre despises the most: She falls into the category of the "plants" — she is unhappy about her life but lacks the courage to do something about it. She hears Clytemnestra scream in the distance and realizes that she has been murdered. Orestes returns and wishes not to speak of the death: "There are some memories one does not share." Electra has not shared in the murder and is not part of Orestes' act; she is not as free as he is. While she sees darkness, Orestes sees a new day dawning. He announces that he is free, but Electra does not feel this freedom; she suffers remorse over the murders, but Orestes feels nothing. He carries his burden with responsibility, and this is why he feels no remorse. He has earned himself the fulfillment of commitment; he possesses himself and his life. Electra loses the ability to see him and begins to suffer from an attack by the flies. But Orestes doesn't care: "What do the flies matter to us?"