What conflict or problem do the people face as the play Oedipus Rex opens?

As the
play  opens, the people face yet another plague that has descended upon
Thebes.  "Black Death" is troubling the city:  crops are failing, livestock is dying,
and women are not able to bear children.  The Priest comes towith a message from the
people--they trust Oedipus's power because he is the one who saved them from the plague of the
Sphinx by solving her riddle, and thus they believe that he can also save them from this plague.
 To get some answers, Oedipus's brother-in-lawhas gone to the oracle at Delphi to get a prophecy
regarding the present plague.  When Creon returns, he says that the oracle has said that they
must rid Thebes of a pollution--the one who is the murderer of the former king Laius.  So, the
quest then becomes rooting out this murderer so that the plague on Thebes can be
lifted.