what walks on four legs in the morning, two legs at noon and three legs in the evening?
Laius and Jocasta have baby Oedipus, but have to send him away from them and have him chained up because of the prophecy that Oedipus would kill his father and marry his mother.
After being taken in by the king and queen of Corinth, Oedipus finds out of this prophecy and leaves, because he does not want any wrong doing to come about. on his travels into thebes, he gets into a quarrel with Laius and kills him.
Oedipus waltzes into Thebes because he could answer the riddle of the sphinx, freeing Thebes from their plague. In doing this, Oedipus is crowned king of Thebes, but something still isn't right in thebes for a while after.
Creon returns from the oracle with the news that the plague in Thebes will end when the murderer of Laius is discovered and driven out.
"...By banishing a man, or expiation of blood by blood..."
Shocked, Oedipus learns, contrary to his expectations, that he is the man responsible for the plague that has stricken Thebes because he is the man who killed his father and slept with his mother.
Because it is now for certain that Oedipus is the man who killed his father and slept with his mother, this discovery drives Jocasta to hang herself and Oedipus to poke out his own eyes, because this was all brought upon by him.