Orestes and The Tutor enter a public square in Argos, an ancient Greek city. Old women come out and offer libations to a large statue of Jupiter in the square. The Tutor attempts to ask the old women for directions, but they run away in fear. He complains that the city is very hot, that it resounds with ugly screams, and that it is full of unfriendly people. Orestes replies that he was born there. The Tutor tries asking more people for directions, but the only one who will talk to him is the Idiot Boy, who cannot say anything coherent.
Jupiter passes by twice and the Tutor insists that this man has been following them. The Tutor complains about the large flies around them as Jupiter enters into the conversation, introducing himself as Demetrios, a traveler who frequently visits Argos. He explains that the flies came to the city fifteen years ago. At that time, King Agamemnon was returning with the Greek fleet. Queen Clytemnestra went out to meet him, accompanied by her lover, Aegistheus. All the Argives knew that the two lovers planned to kill the king, but no one said anything because they wanted to witness violence. They opened their windows and peeked through their curtains out of anticipation, hoping to see blood and hear screams. Jupiter (as Demetrios) says that he did not interfere either, because he was a stranger and because this was not his concern.
Jupiter explains that the gods used the event to teach a moral rather than to punish Aegistheus. They sent the flies as an accusatory symbol and reminder of the Argives's complicity in the murder. Jupiter grabs an old woman walking by and interrogates her about Agamemnon's murder, her sin, and her repentance. He explains to Orestes that morality in the city is upheld through fear. He says this pleases the gods. Jupiter further explains that this day is Dead Man's Day, when every year a man is chosen to scream in the palace to remind the Argives of Agamemnon's death. Orestes asks about Electra, and Jupiter says that she is only a child, but he says that she has a brother who is thought to be dead but who might be alive. He expresses his hope that if the brother, Orestes, is alive, he will not interfere with the lives of the Argives because they must work out their own repentance and live in the favor of the gods. Orestes, he says, is a stranger and cannot help them. To hide his identity, Orestes introduces himself as Philebus.
When Jupiter departs, Orestes mourns his lack of attachment to anything. The Tutor has taught him philosophy and has attempted to teach him that all human morals are relative and that an educated individual should not be committed to any of these morals. As a result, Orestes is completely free of responsibility and commitment. Orestes mourns, however, that nothing is truly his. He was born in Argos, but he has no memories of it; it is not his city and the Argives are not his people. Lacking any attachment, he decides that he has no reason to remain in Argos. The Tutor is glad because he was worried that Orestes might want to kill Aegistheus and take back his father's throne. Orestes says that these are only dreams.
The structure of The Flies reflects Sartre's philosophical message: the play revolves around Orestes's recognition of his freedom. In Act I, Orestes struggles with what he feels is a false freedom—his freedom from attachment and commitment of any sort. In Act III, he has already recognized that he is free and has created his own destiny through action. Act II is divided into two scenes. Scene one shows Orestes making a free decision to act. Scene two shows his action. The structure of the play mirrors Sartre's conception of the structure of freedom. In order to recognize one's freedom, one must let go of the past, make a choice, act on it, and then take responsibility for that decision.
The Tutor's incessant complaining at the beginning is a clever dramatic device. The initial dialogue literally sets the scene. The audience is immediately introduced to the decrepitude of the city by reference to all the senses. The conversation between Orestes and the Tutor touches on the unfriendly people, the buzzing flies, the Idiot Boy with puss leaking from his eyes, the smell of decrepitude, the screams in the background, and the scorching heat of the sun. The vivid descriptions serve to create an atmosphere for the audience that includes both what can be seen and heard on stage and what can only be imagined. By explicitly pointing out that Argos is repulsive to all the senses, Sartre attempts to involve the audience as much as possible with the environment of the play. Like Orestes and the Tutor, the audience is revolted by the conditions of the city and feels estranged from it. By being brought into the same environment as Orestes, the audience is forced to choose the proper course of action along with him.