Sophocles uses foreshadowing to hint at Oedipus's downfall through the prophet Tiresias. When Creon comes back from the oracle at Delphi with the news that the plague in Thebes will end when Laius's murderer is brought to justice, Tiresias is reluctant to speak. He first tells Oedipus that it's just as well if he doesn't tell him what he knows. This communicates the uneasy possibility that whatever Tiresias has to say, it will not be good news for Oedipus.
When Oedipus insists that Tiresias speak, Tiresias still doesn't name Oedipus outright at first; he hints that the person responsible for the plague is in the room. Tiresias says,
I go, but first will tell thee why I came.
Thy frown I dread not, for thou canst not harm me.
Hear then: this man whom thou hast sought to arrest
With threats and warrants this long...
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