The play begins in the royal house of Thebes. The stage directions state that Oedipus solved the riddle of the Sphinx many years earlier and has since ruled as king of Thebes. As the play begins, a procession of miserable-looking priests enters. Oedipus follows soon after, walking with a slight limp and attended by guards.
Oedipus limps because Laius and Jocasta (who he doesn't know are his parents) pinned his ankles together when he was an infant to thwart the prophecy that he would kill Laius (they failed). The limp marks Oedipus's fate, even though he does not know it yet.
Oedipus asks the priests why they have come. He knows that the city is sick with plague. He tells them they can trust him to help in any way he can. In a moving speech, a priest tells Oedipus the city's woes: the crops are ruined, cattle are sick, women die in labor and children are stillborn, and people are perishing from the plague. The priest begs Oedipus to save Thebes, just as Oedipus once saved it from the Sphinx.
Oedipus says he knows of the trouble and has been trying to think of a solution. He has already sent Creon, his brother-in-law, to the oracle at Delphi to find out what the god Apollo advises. Just then, the priest notices that Creon is returning from this mission.
Oedipus is a vigorous and active leader. He has already anticipated the priests' request for help and has done what a good Greek ruler should do—seek advice from an oracle.
Creon tells Oedipus and the assembled priests the words of the god Apollo, according to the oracle. Before Oedipus became king, the previous king, Laius, was murdered, and his murderer was never discovered. According to the oracle, the killer lives in Thebes. He must be caught and punished in order to stop the plague.
As when he faced the Sphinx, Oedipus is presented with a puzzle to solve: the identity of Laius's murderer. Shame was believed to have real-world consequences. The plague results from the shame of not punishing Thebe's former king's murderer.
Oedipus asks Creon about the circumstances of Laius's death. Creon says that Laius left the city to consult the oracle of Apollo and never returned. Only one eyewitness to the murder survived and returned to Thebes. This man claimed that a band of thieves killed the king. Oedipus asks why no one tried to find the murderers. Creon responds that, at the time, Thebes was under the Sphinx's curse. Oedipus then promises that he'll take on the task of finding the murderer.
Oedipus is a hero and a man of action. Had his king been murdered, nothing would have stopped him from finding the murderer, just as he is promising to let nothing stop him now. Creon is more pragmatic and less inclined to take action. Having just escaped the Sphinx, searching out Laius's murderer seemed impossible to Creon.
The chorus, which has not heard the news from the oracle, enters and marches around an altar, chanting. The chorus catalogs the misfortunes of Thebes and calls on many gods by name to come to the city's aid.
Oedipus orders anyone who knows anything about Laius's murderer to speak, in exchange for light treatment and possibly a reward. But, Oedipus declares, if anyone has useful information and does not speak, the citizens of Thebes must banish this person. Oedipus curses the murderer—"Let that man drag out his life in agony, step by painful step." He adds that even if the murderer ends up being a member of his own family, he or she should receive the same harsh banishment and punishment.
Oedipus acts quickly to find the killer. He thinks he knows what happened—thieves killed Laius—but is actually blind to the truth. Acting blindly, he curses himself. Greek audiences would have known the Oedipus story, and so in this scene Oedipus would seem to be describing his own fate, or even bringing this fate upon himself.
Oedipus criticizes the people for not hunting more vigorously for Laius's killer. He says he will fight for Laius as if Laius were his own father. Oedipus curses anyone who defies his orders. The leader of the chorus suggests that Oedipus send for Tiresias, the blind seer. Oedipus announces that he has already done so. Soon, blind Tiresias arrives, led by a boy.
Another example of Oedipus's strong leadership. He's one step ahead of the suggestions his subjects make to him and has already sent for Tiresias. Yet in saying he would fight for Laius as if he were his own father, Oedipus further displays his own blindness to the truth.