Oedipus Rex and that deal with the story of Oedipus, "Oedipus Rex" was the second to be written. However, in terms of the chronology of events that the plays describe, it comes first, followed by "Oedipus at Colonus" and then "Antigone". Prior to the start of "Oedipus Rex", Oedipus has become the king of Thebes while unwittingly fulfilling a prophecy that he would kill his father, Laius (the previous king), and marry his mother, Jocasta (whom Oedipus took as his queen after solving the riddle of the Sphinx). The action of Sophocles' play concerns Oedipus' search for the murderer of Laius in
Oedipus Rex the prophecy that the king had sought to avoid by exposing Oedipus at birth is fulfilled. Before arriving at Thebes, Oedipus encounters the Sphinx, a legendary beast with the head and breast of a woman, the body of a lioness, and the wings of an eagle. The Sphinx was sent to the road approaching Thebes as a punishment from the gods, and would strangle any traveler who failed to answer a certain riddle. The precise riddle asked by the Sphinx varied in early traditions, and is not stated in "Oedipus Rex", as the event precedes the play; but the most