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 at Colonus of guilt; the fact that Oedipus is "rationally innocent" – that he sinned unknowingly – decreases his guilt, allowing his earthly sufferings to serve as sufficient expiation for his sins. Darice Birge has argued that "Oedipus at Colonus" can be interpreted as a heroic narrative of Oedipus rather than a tragic one. It can be viewed as a transitional piece from the Oedipus of "Oedipus Rex" whose acts were abominable to the Oedipus we see at the end of "Oedipus at Colonus", who is so powerful that he is sought after by two separate major cities. The major image used