There is little plot as such; instead, the bulk of the play consists of rich dialogues that show how the citizens of Thebes and their king Eteocles feel about the threat of the hostile army before their gates. Dialogues show aspects of Eteocles' character. There is also a lengthy description of each of the seven captains that lead the Argive army against the seven gates of the city of Thebes as well as the devices on their respective shields. Eteocles, in turn, announces which Theban commander he will send against each Argive attacker. Finally, the commander of the troops before the seventh gate is revealed to be Polynices, the brother of the king. Then Eteocles remembers and refers to the curse of their father Oedipus. Eteocles resolves to meet and fight his brother in person before the seventh gate and exits. Following a choral ode, a messenger enters, announcing that the attackers have been repelled but that Eteocles and Polynices have killed each other in battle. Their bodies are brought on stage, and the chorus mourns them.
Due to the popularity of Sophocles' play Antigone, the ending of Seven against Thebes was rewritten about fifty years after Aeschylus' death. While Aeschylus wrote his play to end with somber mourning for the dead brothers, it now contains an ending that serves as a lead-in of sorts to Sophocles' play: a messenger appears, announcing a prohibition against burying Polynices; his sister Antigone, however, announces her intention to defy this edict.
The seven attackers and defenders in the play are: