The protagonist of the story is the son of royalty in Thebes. Before the story even begins, the audience knows that King Laius has been murdered on his way to consult an oracle in Delphi. In addition, it is known that Oedipus has been proclaimed as king of Thebes after he solves the riddle of the terrorizing Sphinx. The information that we are given allows for dramatic irony throughout the story; we know vital information that is unknown by the characters of the play.
After a prophecy is revealed about Oedipus's fate, Jocasta recants a story about how she was told that her son was going to kill his father and sleep with his mother which she assumes never came true. As the story progresses, Oedipus, curious about his past and true origins, invites a shepherd to tell the story of his youth.
Oedipus learns that the shepherd was given Oedipus as a boy and took him back to Corinth to the king and queen to be raised as royalty proving that the royalty of Corinth were not his biological parents. Oedipus learns that after he ran away from Corinth, he met his biological father, King Laius, who he killed after an argument. Next, he became king after solving the sphinx's riddle and married his mother, who was Laius’s wife. Jocasta, overridden with emotion, hangs herself, and Oedipus gouges out his own eyes with pins from her dress.