As the play Oedipus Rex 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 to Oedipus with 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-law Creon has 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.