The play begins when a priest confronts King Oedipus at his palace in Thebes, informing him of a terrible plague that was occurring upon the Thebans. Oedipus responds by sending Creon to the oracle at Delphi to bring back more information. Creon informs Oedipus that King Laius has been murdered, and that the plague is a manifestation of the fact that Laius's murderer is unknown. In order to rectify the situation, Oedipus vows to put the murderer to justice, and he orders anyone who knows who it is to come forth.
Oedipus consults with the blind prophet Teiresias for answers. Teiresias claims that Oedipus himself was the murderer, a claim that outrages the king. Oedipus furiously blames Creon, believing he made Teiresias blame Oedipus to undermine his power.
When Creon comes back Oedipus threatens him with execution, but Choragos convinces him otherwise. Later Iocasta comes to soothe Oedipus, reasoning that prophets were false in their predictions. She informs Oedipus of an oracle she received that stated Laius was to be killed by his own son and she (Iocasta) would sleep with her son. Oedipus then remembers of a crucial detail about Laius's death: it took place at a crossroads, and Oedipus remembers that he was there. Oedipus gathers more details and begins to fear that Teiresias's accusation might actually prove to be true.
In an attempt to ease his qualms Oedipus intends to meet with one surviving witness of the murder: a shepherd. He explains to Iocasta that years ago at a banquet in Corinth, a man drunkenly accused Oedipus of not being his father's son. Angered and distraught over this, he went to the oracle at Delphi to test its factuality. Instead of the confirmation that he was indeed his father's son, Oedipus received a chilling prophecy stating that he would murder his father and sleep with his mother. With this outrageous prognosis in mind, Oedipus concluded that he must leave Corinth to prevent it from happening. On his way however, Oedipus encountered a carriage that aggravated against him on the road. In retaliation Oedipus murdered the group of men, including the man that possibly could have been Laius himself.
After recounting his experience, Oedipus posits that since it was said that several robbers killed Laius, it could be possible that Oedipus had not actually killed his father. Soon a man arrives from Corinth bringing to Oedipus the message that his father recently passed away. Oedipus then rejoices happily, because it seems as if the prophecy was false after all.
However, it emerges that the messenger himself was a shepherd, and previously he was given a baby from another shepherd. It is later known that the shepherd who gave the baby to the shepherd present was actually the one witness to the murder of Laius. Oedipus calls for this shepherd to come forth, and after forcefully commanding him to reveal the truth, it is learned that the shepherd received the baby from Iocasta, because she feared for the prophecy. However, instead of leaving the baby to die on the mountainside as told, the shepherd passed the baby on to another shepherd, and finally Polybus adopted him. The baby himself was Oedipus.
By now Iocasta and Oedipus have realized the truth, and Iocasta runs out. Oedipus curses himself for the atrocity he committed. Iocasta hangs herself in her bedroom, and Oedipus despairs over his life and threatens suicide. Once he sees Iocasta's body, he takes off the golden brooches on her dress and plunges them into his eyes, effectively blinding him.