The Narrator greets the audience, explaining the nature of the drama they are about to see, and setting the scene: Thebes is suffering from a plague, and the men of the city lament it loudly. Oedipus, king of Thebes and conqueror of the Sphinx, promises to save the city. Creon, brother-in-law to Oedipus, returns from the oracle at Delphi and declaims the words of the gods: Thebes is harboring the murderer of Laius, the previous king. It is the murderer who has brought the plague upon the city. Oedipus promises to discover the murderer and cast him out. He questions Tiresias, the soothsayer, who at first refuses to speak. Angered at this silence, Oedipus accuses him of being the murderer himself. Provoked, Tiresias speaks at last, stating that the murderer of the king is a king. Terrified, Oedipus then accuses Tiresias of being in league with Creon, whom he believes covets the throne. With a flourish from the chorus, Jocasta appears.

Jocasta calms the dispute by telling all that the oracles always lie. An oracle had predicted that Laius would die at his son's hand, when in fact he was murdered by bandits at the crossing of three roads. This frightens Oedipus further: he recalls killing an old man at a crossroads before coming to Thebes. A messenger arrives: King Polybus of Corinth, whom Oedipus believes to be his father, has died. However, it is now revealed that Polybus was only the foster-father of Oedipus, who had been, in fact, a foundling. An ancient shepherd arrives: it was he who had found the child Oedipus in the mountains. Jocasta, realizing the truth, flees. At last, the messenger and shepherd state the truth openly: Oedipus is the child of Laius and Jocasta, killer of his father, husband of his mother. Shattered, Oedipus leaves. The messenger reports the death of Jocasta: she has hanged herself in her chambers. Oedipus breaks into her room and puts out his eyes with her pin. He departs Thebes forever as the chorus at first vents their anger, and then mourns the loss of the king they loved.