Since tragedies were based on widely-known myths or famous historical events, the audience would know the characters and outline of the story they were about to see. Most surprises, therefore, did not come from the plot, although playwrights could introduce innovations into the story. In seeing a play about Antigone, the audience would already know that this story came from the cycle of myths about the city of Thebes, one of Athens' rivals in the 5th century. The story is set a few generations before the Trojan War, which the ancients set in 1184 BCE. Laius, the king of Thebes, received a prophecy that his son would kill him. To avoid this outcome, when a child was born to Laius and his queen, Jocasta, he had the baby exposed on Mount Cithaeron, at the edge of his kingdom; he nailed the child's feet together as an extra precaution (a common way to get rid of unwanted infants throughout the historical period). Unfortunately for Laius, the baby survived and was raised as a prince of the city of Corinth with the name Oedipus, which means “swollen feet” in Greek.
Many years later, Oedipus, not knowing his true birth, met Laius on the road. Without either man knowing the identity of the other, an argument arose, and Oedipus unknowingly killed his father. At that point, Thebes was being terrorized by the Sphinx, a monster with the head of a woman, body of a lion, and wings of an eagle. The Sphinx was particularly famous for telling everyone she encountered a riddle; when they could not answer it, she devoured them. This was her riddle: “What walks on four legs in the morning, two legs in the afternoon, and three legs in the evening?” The person to solve this riddle was Oedipus, the answer being ‘man' (who crawls as a baby, walks on two legs as an adult, but leans on a cane in his old age). Her riddle solved, the Sphinx threw herself from a cliff, and Oedipus was crowned king of Thebes and married to the recently widowed queen, his own mother Jocasta. Years passed before the gods brought the incest to light, after which Jocasta committed suicide and Oedipus blinded himself, living the rest of his life as a homeless wanderer.
Oedipus and Jocasta had several children together; when his sons disobeyed him, Oedipus cursed them, thus continuing the family's wretched destiny. Oedipus then died either at Thebes or in exile; the myths are inconsistent. Regardless, a quarrel arose between Oedipus' sons, Eteocles and Polynices. The latter, although older, was exiled and journeyed to the powerful city of Argos, where he won the favor of the Argive king. The king betrothed his daughter to Polynices, who returned to Thebes at the head of an Argive army. The panic-stricken city was defended by Eteocles and six others, who met Polynices and six heroes (the famous “Seven Against Thebes,” subject of a play by Aeschylus) from the rest of Greece at each of the city's seven gates. The Thebans were victorious and the Argive army left the city. Polynices and Eteocles, however, were both slain, leaving the kingship to Jocasta's brother Creon. He also took custody of Oedipus' remaining children, two young daughters named Antigone and Ismene.