At the beginning of the play, the city of Thebes is cursed terribly. Citizens are dying from plague, crops fail, women are dying in childbirth and their babies are stillborn. Some priests come to the royal palace to ask for help from Oedipus, the current king of Thebes who once saved them from the tyranny of the terrible Sphinx. By this time, Oedipus has sent his brother-in-law, Creon, to the oracle of the god Apollo to seek advice from divine sources. But before Oedipus had ever arrived in Thebes, the previous king, Laius, was murdered under mysterious circumstances and the murderer was never found.
When Oedipus arrived in Thebes and saved the city, he was made king and married the widowed queen, Jocasta, sister of Creon. Now Creon returns with the oracle’s news: for the plague to be lifted from the city, the murderer of Laius must be discovered and punished. The oracle claims that the murderer is still living in Thebes. Oedipus curses the unknown murderer and swears he will find and punish him. He orders the people of Thebes, under punishment of exile, to give any information they have about the death of Laius.
Then, Oedipus sends for Tiresias, the blind prophet, to help with the investigation. When Tiresias refuses to tell Oedipus what he has seen in his prophetic visions Oedipus accuses Tiresias of playing a part in Laius’s death. Tiresias grows angry and says that Oedipus is the cause of the plague—he is the murderer of Laius. As the argument escalates, Oedipus accuses Tiresias of plotting with Creon to overthrow him, while Tiresias hints at other terrible things that Oedipus has done.
Convinced that Creon is plotting to overthrow him, Oedipus declares his intention to banish or execute his brother-in-law. Jocasta and the chorus believe Creon is innocent and beg Oedipus to let Creon go. He relents, reluctantly, still convinced of Creon’s guilt. Jocasta tells Oedipus not to put any stock in what prophets and seers say. For as an example, she tells him the prophecy she once received—that Laius, her first husband, would be killed by their own son.
And yet, Laius was killed by strangers, and her own infant son was left to die in the mountains. But her description of where Laius was killed—a triple-crossroad—worries Oedipus. It’s the same place where Oedipus once fought with several people and killed them, one of whom fit the description of Laius. Now, with that new information, Oedipus is left with an uncertain question that haunts him. Could Teresias be right? Could he, Oedipus himself, be the true murderer of Laius?