At the beginning of the play, the Chorus has come to Oedipus's royal palace in Thebes, and when Oedipus comes out to speak to them and find out what is wrong, the leader tells him,
[...] our ship of State,
Sore buffeted, can no more lift her head,
Foundered beneath a weltering surge of blood.
A blight is on our harvest in the ear,
A blight upon the grazing flocks and herds,
A blight on wives in travail; and withal
Armed with his blazing torch the God of Plague
Hath swooped upon our city emptying
The house of Cadmus, and the murky realm
Of Pluto is full fed with groans and tears.
There are several problems in Thebes that are sorely affecting its citizens. The Chorus leader says that these problems are so many and so destructive that the very livelihood of Thebes is threatened. First, something is ruining the crops so that the food seems to rot in the field. Second, some illness is killing the livestock, and, third, women in labor are having terrible trouble, perhaps even dying during childbirth. These plagues have descended on the city (caused by Apollo, the god associated with both plague and prophecy, which shortly becomes relevant in the play), causing a great deal of death so that the Underworld (the realm of Pluto, also called Hades) is filling up with depressed deceased victims.
As the play Oedipus Rex, by Sophocles, opens, the people of Thebes are dealing with a kind of plague—in this case, a famine. Their crops will not grow, and people are dying. Oedipus sends Creon to the Oracle of Delphi to find out what they should do, and Creon comes back with the message that the man who is responsible for the death of the former ruler, King Laius, must be exiled or killed. The plague will continue until this is done. Oedipus is confident he can find the murderer and rid the town of the famine, and the people believe he can, too, because of his earlier success at solving the "Riddle of the Sphinx." Of course, Oedipus does not initially realize that he is the guilty one. He does find the answer, and in it, he also finds his fate.