Laius, son of Labdacus, King of Thebes, had been told at Delphi by the oracle that a son would be born to him who should slay him. When his wife Iocasta bore a son, the babe was given by its mother to a Theban shepherd, to expose on Mount Cithaeron. This man, in pity, gave it to a Corinthian shepherd whom he met in the hills, who took it to Corinth; and there the child was brought up as the son of King Polybus and his wife Merope.
Years went by. Once at a feast the young Oedipus was taunted with not being really the son of Polybus. He went to ask the oracle at Delphi; and was told that it was his destiny to slay his father and to wed his mother. He resolved never to go near Corinth again, and took the road leading eastwards into Boeotia. On his way he met Laius, King of Thebes, at the 'Branching Roads' in Phocis, without knowing who he was. A quarrel occurred: Oedipus slew Laius, and three of his four attendants. The fourth, who escaped, was the Theban shepherd who in old days had received the infant from Iocasta.
Oedipus continued his journey, and reached Thebes at the time when it was being plagued by the Sphinx. He guessed the monster's riddle, and the Sphinx hurled herself from a rock. Oedipus was made King of Thebes, and married Iocasta. Soon afterwards the shepherd sought an audience of the Queen, and earnestly prayed that he might be sent to tend flocks in certain distant pastures. She readily granted the boon; it was a small thing for an old and faithful servant to ask.
About sixteen years have passed since then, and Iocasta has borne two sons and two daughters to Oedipus.
But now a great calamity has visited Thebes: there is a blight on the fruits of the earth: a pestilence is desolating the city. While offerings are made at the altars, a band of suppliants, old and young, is led by the Priest of Zeus into the presence of the wise King. He, if any mortal, can help them.