Oedipus the King by Sophocles (429 BCE)

The story of Oedipus was well known to the audience that Sophocles was writing for.  The play opens in the middle but everyone in Sophocles time knows the background.

The story that predates the play is that Jocasta and Laius have a son who is predicted to kill his father and marry his mother.  They do what any sensible Greek family at the time appears to have done--they nailed his feet together and gave him to a shepherder to leave on the mountainside.  They did not factor in the shepherder's free will--he gave the baby to the childless king of Corinth, and Oedipus (which apparently means 'swollen feet') survives.  As a young man Oedipus is told of the prophesy that prompted his parents to abandon him to the elements--but no one tells him these are not his real parents, so he makes the fateful mistake of leaving Corinth, where upon he indeed kills his father, marries his mother, and fathers four children with her.

How does it all come to light?  Those are the events that this play focuses on.  A plague has befallen Thebes and in order to end it, the oracle tells Creon the murder of Laius must be expelled--Oedipus, not realizing it is he, vows to get to the bottom of the story, but as each witness to a different piece of the story is brought in, there is a slow dawning, first to Jocasta and then to Oedipus himself that the prophesy that they both worked to avoid has indeed come true.  Jocasta kills herself and Oedipus scratches his eyes out with Jocasta's pins.