Oedipus Rex is a play written by Sophocles set in the ancient Greek. The story is a tragedy. I will try to keep the story short and precise. So there was a place named Thebes. The people of Thebes were in terror of a creature called sphinx. Sphinx had a body of a lion, face of a female and feather and claws of a bird. Her condition was if anybody will solve her riddle she will leave Thebes. Her riddle was- “What is it that has four legs but requires a support, then when it has two legs it doesn't require anything, but ends up with three legs.” People had failed to answer it. As a result they were eaten up by the sphinx. A boy named Oedipus  from Corinth decided to face the Sphinx. He gave the correct answer- Human. The sphinx flew away and as a result Oedipus was made the king of Thebes. He was married to the already prevailing queen Jocasta, the widow of the ex king Laius. Later Jocasta had two daughters with Oedipus. 

Everything was going great until severe plague ravaged the land of Thebes. People came wailing to Oedipus. A rumor started that the ex king's death isn't avenged yet that is why Thebes is suffering. A blind prophet Tiresias was called upon. He said the land of Thebes had become barren because the rumors are true. On investing more about who is the killer, how does he look, Tiresias advised the king to not proceed with the investigation. Oedipus thought that maybe Tiresias is the killer that is why he is giving such advices when the people of his own land are dying. An argument heated between the two and Tiresias said it's King Oedipus who killed King Laius. Stunned by such allegation Oedipus showed the doors to Tiresias. 

Seeing Oedipus so angry Jocasta tried to calm him down, telling him that everything such prophet says aren't true. She tells him that years ago the same prophet had made a prophecy which never came true. The prophecy was a child will be born to King Laius and Jocasta which will grow up to kill his own father and marry his own mother. As soon as the child was born, the king ordered to kill him. But the heart of the mother can never be that stone hearted so she took her baby and left him in the jungle, with no idea what happened to him. Also Laius was killed on his way to some other kingdom by some village man. So the prophecy turned out to be wrong. There is nothing to worry. 

But the last sentence of Jocasta that- Laius was killed on his way to some other kingdom intrigued Oedipus. He asked more and later realized that that village man who killed Laius was himself only. He had gotten into an argument with the soldiers and had killed them along with Laius. But he wasn't Laius's son, he was Polybus's (a shepherd from Corinth) son. A messenger was sent to Corinth to call Polybus but he returned with message that Oedipus was found on a mountain as a baby to Polybus he wasn't his biological father. Which confirmed that prophecy had come true. Oedipus was King Laius's and Jocasta's son who had killed his own father and married his own mother. Jocasta failed to take the shock and hanged herself in her room. Tragedy had fallen upon Oedipus he took the dead body of Jocasta down, removed long gold pins from her dress and bulged them into his eyes and went into exile.