An unexpected messenger now arrives from Corinth and asks to speak with Oedipus, upon which he is introduced to Jocasta and offers her his blessing. He says that he brings good news for the House of Thebes, though the news will be bittersweet. Jocasta urges him to elaborate, upon which she discovers that King Polybus is dead and Oedipus is to be crowned king of Corinth. Jocasta sends a servant to quickly fetch her husband and marvels aloud that Oedipus seems to have evaded the prophecy after all.

Entering from the palace, Oedipus demands to hear these tidings for himself, and the Messenger reiterates that Polybus has died of old age and natural causes. Triumphant, Oedipus mocks the worthless words of the prophets, which he claims have all come to nothing. Yet he hesitates, pondering the second part of the prophecy, which stated that he would sleep with his mother. Jocasta dismisses this, however, assuring him that there is no real substance to this and that no man on earth can predict the future.

Oedipus remains unsure and points out that his mother is still alive, hence why he still fears the prophecy. The Messenger is curious to understand and presses Oedipus to explain his fears, whereupon Oedipus reveals that he is destined to bed his mother and kill his father. He explains that this is why he has avoided the city of Corinth. The Messenger tells him that he has nothing to fear, because in fact Merope and Polybus are not his true parents. He goes on to describe how he himself found Oedipus as a baby on the mountainside and delivered him to the king and queen of Corinth, who were without a child.

The Messenger says that Oedipus’s ankles were pinned together as a baby, which led to him being named Oedipus—meaning “swollen feet” in Greek—and that a servant from the house of Laius gave the baby over to a man. Oedipus demands to know whether this man is still living and turns to the Chorus, imploring them to tell him of his whereabouts. The Chorus confirm that this old man is the same shepherd whom they recently sent for as the sole witness to the murder of Laius. Jocasta now becomes defensive and begs Oedipus to stop pursuing this line of inquiry. When he refuses, thinking that Jocasta only cares whether or not he is of noble birth, she exclaims that he is doomed and storms offstage.

In the silence that follows, the Leader of the Chorus wonders aloud what may come of this. However, Oedipus is adamant that he must know the truth about his identity and asserts that he will never be ashamed of his origins. The Chorus rally themselves to support him here, naming Mount Cithaeron as Oedipus’s mountain mother and calling on the gods Apollo, Pan, Hermes, and Dionysus to unlock the mystery of his birth. At this point, the shepherd is seen approaching, and although Oedipus doesn’t recognize him, the Leader of the Chorus identifies him as the former servant of Laius.

The Messenger from Corinth is also forced to identify the old Shepherd, after which Oedipus interrogates him about his work and connection to the former king. He then asks him if he recognizes the Messenger from Corinth. The old man struggles to remember, and the Messenger recalls for him the six months they spent together grazing their flocks on the slopes of Mount Cithaeron. When the Shepherd’s memory remains unclear, the Messenger reminds him of the baby he gave him long ago and shows him that Oedipus was once that same baby. At this, the old man reacts explosively and curses the Messenger for bringing this information to light.

Oedipus has his guards seize the Shepherd and, under threat of torture, asks him again whether the story is true. Reluctantly, the old man accepts that it is so and finally, when Oedipus threatens to kill him, acknowledges that the baby came from the house of Laius. Still, Oedipus forces the terrible truth to be spoken aloud, and bit by bit, he drives the Shepherd to admit that the child belonged to the king and queen and was given to him to dispose of by the queen herself. Pitying the child, he could not kill him, but gave him to the Messenger of Corinth to be taken far away from Thebes.

Realizing his fate, Oedipus cries out in despair and exclaims that the truth has now been revealed—that he was cursed from birth to murder his father and bed his own mother. He exits through the palace doors.