For the plot of Antigone, Sophocles drew material from the familiar legends of Oedipus, the King of Thebes, and also from an earlier play by Aeschylus called Seven Against Thebes.
The plot of a Greek tragedy usually consisted of five parts: the prologue, the Parodos, the five Epeisodia (episodes), the five stasima and the Exodus (or epilogue). Sophocles follows the conventional pattern of plot construction with very little deviation from the norm.
The Prologos (literally ‘fore-word’) forms the prologue to the actual play. It is the part preceding the first entrance of the Chorus and usually consists of a monologue (or dialogue) setting forth the subject matter of the tragedy and the basic situation from which it starts. In early Greek tragedies, the Chorus entered first and performed this function of exposition. Sophocles prefers a later method in Antigone, by making Antigone reveal her decision to bury Polynices to her sister, Ismene