Jocasta belongs to the Theban royal line and is the daughter of Menoeceus and sister of Creon in major later traditions. Some mythographers connect the disaster of Laius' house with an earlier offence against Chrysippus, son of Pelops, and a curse placed upon Laius. That prehistory is a later strand and should not be treated as the universal starting point of the Oedipus myth. Sophocles instead centres the tragedy on Apollo's oracle that a son of Laius will kill his father.

The storm broke with the birth of Jocasta's first child, a son. Laius had already consulted the oracle of Delphi, the greatest sanctuary in Greece, where the priestess of Apollo spoke the words of the god, and the answer had been plain: if Laius fathered a son, that son would kill him. So when Jocasta bore a boy, the king acted at once and without mercy. He pierced the infant's ankles with an iron pin and handed the child to a shepherd with orders to leave it on Mount Cithaeron, the wild mountain ridge between Thebes and Corinth, where exposure and the wolves would finish the work. But the shepherd looked at the bleeding little feet and could not do it. He passed the baby to a fellow herdsman from Corinth, who carried the foundling to the childless Polybus, the king of Corinth, and his queen Merope. They raised the boy as their own prince and named him Oedipus, Swollen Foot, for the wounds in his ankles. Jocasta grieved and believed her son dead, and the royal couple of Thebes lived on, the curse apparently cheated.

The curse was only waiting. Years later Oedipus, now grown, heard a drunken taunt that he was not the true son of Polybus and Merope, and in his distress he travelled to Delphi to ask the oracle who his parents were. The priestess gave him no answer to that question, only a sentence of horror: he would kill his father and marry his mother. Oedipus loved Polybus and Merope, and believing them his true parents, he resolved never to return to Corinth and so never to fulfil the prophecy. He set out on foot toward Thebes, and at a narrow place where three roads crossed, in a country of rocks and dust between Delphi and Thebes, he met a party of travellers in a carriage. It was Laius, coming from Thebes on his own journey to Delphi. A quarrel broke out over right of way on the narrow road, a herald struck Oedipus, and in his anger Oedipus killed the old man and all his companions except one slave, who escaped into the mountains. Neither father nor son knew the other. The son whose death Jocasta mourned had just killed the husband she waited for, and the curse of Pelops had claimed its first victim at a dusty crossroads far from home.

Jocasta did not even receive the news. Before the lone survivor could bring word to Thebes, a new terror had fallen on the city. The Sphinx, a monster with the face of a woman, the body and claws of a lion, and the wings of a great bird, had taken up her seat on a cliff above Thebes, sent by the gods to punish some offence of the city. She stopped every traveller and put her riddle to them: what creature walks on four legs in the morning, two legs at noon, and three legs in the evening? When no one could answer, she seized them and devoured them, and Thebes began to starve behind its walls. Creon, the brother of Jocasta, ruled as regent in the absence of a king, and in desperation he proclaimed that whoever saved the city from the Sphinx would receive the throne of Thebes and the hand of the widowed queen. Oedipus came to the cliff, heard the riddle, and answered without hesitation: man, who crawls on all fours as an infant, walks upright in the strength of his prime, and leans on a staff in old age. The Sphinx, defeated, threw herself from the rock and died. Oedipus entered Thebes as king and saviour, married Jocasta, and fulfilled the oracle he had spent his whole life running from. In the years that followed the marriage prospered, and Jocasta bore four children: two sons, Eteocles and Polynices, and two daughters, Antigone and Ismene. The throne was secure, the queen was honoured, and the past seemed buried on a mountain.

It was not buried; it was waiting for daylight. Many years later a blight fell on Thebes, cattle dying in the fields, women bearing dead children, and a burning plague in the streets. Oedipus, desperate to save his people, sent Creon to Delphi, and Creon returned with the god's answer: the city harboured a pollution, the unpunished murderer of King Laius, who still lived within the walls. Oedipus swore before the whole city that he would hunt the killer down and curse him with exile or death. Jocasta watched her husband's fury with a growing unease, and when the blind prophet Tiresias, the seer of Thebes, was summoned and at first refused, then darkly accused Oedipus himself, Jocasta stepped forward to calm the king. Oracles, she said, were worthless. Consider her own life: an oracle had told Laius that his son would kill him, yet Laius had certainly been murdered by strangers at a place where three roads meet, and as for his son, he had died as an infant on the mountain with his ankles pinned together. She was describing, to the man who stood before her, the very journey and the very killing that had brought him to her door. At that moment a messenger arrived from Corinth with the news that Polybus had died, and Oedipus rejoiced, thinking the prophecy broken. But then came the blow: Oedipus was not Polybus's son at all, only a foundling, a baby handed over on Mount Cithaeron by a shepherd of Thebes. Jocasta went white. She begged Oedipus to abandon the search, to ask no more questions, and then she rushed into the palace, into her chamber, and shut the doors.

The last pieces fell into place with merciless speed. The old shepherd was found, the very man who had taken the pin-pierced infant from Laius's own hands, and under threat he confessed: the child had lived, had been given to the Corinthians, had become the man now standing king of Thebes. Oedipus understood at last that the traveller he had killed at the crossroads was Laius, his father, and that the queen who had shared his throne and borne his four children was his mother, and that the pollution the oracle demanded he purge was himself. From inside the palace a servant burst out with the final news: Jocasta had locked herself in her room and hanged herself. Oedipus tore through the doors, cut her down too late, and in his agony he took the golden brooches that pinned her robe and drove them into his own eyes, declaring that the eyes which had failed to see the truth should never look upon the sun again. In another telling of the story, the queen survived the revelation and lived on to see her two sons, Eteocles and Polynices, tear the kingdom apart with their quarrel, and she died trying in vain to make peace between them before the war that killed them both. But the older and grimmer tradition gives her no such afterlife: in the Odyssey, the oldest of the Greek epics, she is named Epicaste, and there the gods made the truth known openly, and she hanged herself above the marriage bed, leaving Oedipus to bear a grief no mortal can measure.

What follows the revelation depends on the poet. In Homer's Odyssey, Epicaste hangs herself and Oedipus remains king in Thebes under the burden of the gods' punishment. Sophocles also makes Jocasta hang herself and later develops Oedipus' exile in a separate play. Euripides' Phoenician Women preserves a radically different branch in which Jocasta survives the revelation and lives to confront the war between Eteocles and Polynices. These variants became foundations of later tragedy and, much later, the name of Oedipus was borrowed by psychoanalysis for Freud's Oedipus complex. None of these later uses removes the central ancient fact: different poets reshaped Jocasta's ending for different dramatic purposes.