Plot in Oedipus Rex
Sophocles creates a chain of communication that Oedipus must go through to obtain information. This creates difficulties for Oedipus for two reasons. First, it makes the flow of information slower, and facts about Oedipus’ life do not reach him until after they would be of use to him. Second, Oedipus does not know whether he can trust the second-hand information he receives. He struggles with coming to terms with the truth, and his doubts about what others tell him are a main source of tension in the play.
Oedipus believes that his ascent to rule over Thebes happened by chance, not of his own volition or through his own actions but by an act of the gods. The conflict between fate and free will, as well as the difficulty to discern between them at times, provides tension as the play progresses.