What Aristotle sees as the great achievement of the playwright here is the proper choice of the dramatic plot from within that story, a mythos that has a clear beginning, middle, and end which will serve as a ritual process for the city’s purgation (catharsis). The play begins with the city of Thebes suffering from a catastrophic plague. The savior king, Oedipus, is approached by the chorus of elders who ask for salvation from this situation. Oedipus informs them that he has sent his brother-in-law Creon to the oracle of Apollo at Delphi to determine the cause of the plague. Creon returns and announces that the city is under a curse because the murderer of the old king, Laius, has never been found. Oedipus, in a grand gesture vows to find the murderer, whom he curses. One can only admire the effectiveness of this beginning. The audience must have been gripped by the pity and fear described by Aristotle as the murderer, unknown to himself, the source of the town’s pollution, vows to destroy himself. This is true tragic irony.

The middle of the play is called the agon, from which we derive the word agony, which describes the ordeal of the protagonist Oedipus, who is also, unwittingly, the antagonist of his own city. The agon involves a struggle between many opposites, but primarily between fate and free will, a struggle inherent in the whole tragic saga of Thebes, and between self-knowledge and the lack of self-knowledge. Thebes cannot return to life, the destructive pollution cannot be removed, until Oedipus can “see” who he is. It is worth remembering here as Sophocles and his audience certainly did, that one of Apollo’s mottos was “Know thyself.”

Naturally, as clues begin to arrive, Oedipus does all he can to remain “in denial” of himself. One of his weapons will be his own position as king and once the savior of his city. But there is also the overweening pride (hubris) derived from that perceived position. He calls on the blind prophet Tiresias for information about the murder, but the prophet refuses to speak. This so infuriates the king that he threatens the old man. In anger Tiresias says, in effect, “You are the murderer.” Oedipus more and more loses control. He accuses Creon of conspiring against him with Tiresias. Tiresias leaves saying that the discovered murderer will be a native of Thebes, the killer of his father, the husband of his mother, and the brother and father of his own children. Oedipus threatens Creon, but Jocasta tries to calm him, reminding him that he cannot be the son of Laius or his murderer, as the former king had been killed by others at a crossroad.

Now things begin to emerge in the mind of Oedipus; he begins to accept his identity. He tells Jocasta of his road-rage conflict and of his killings there. A messenger arrives and tells how the baby with the swollen feet had been given to the king of Corinth. A witness to the crossroad killing has survived. Oedipus is revealed for who and what he is.

The resolution at the end of the play is almost inevitable. The sins here, even if committed without knowledge, cannot be forgiven. Pollution, whatever its source, must be removed. Jocasta goes into the palace and hangs herself. Oedipus takes the pins from her dress and blinds himself. Now, like Tiresias, he lacks sight, but has insight. He knows who he is, and Thebes can return to normalcy under the leadership of Creon.

The mythos of the play ends, but the story goes on, providing material from which at least two other plots—that of the Colonus play and that of Antigone—would be extracted.