The most important thing to remember about the end of Libation Bearers is that this play is only Part 2 of a trilogy of tragedies known as the Oresteia. In guide to Agamemnon, the first play in this trilogy, Clytemnestra has just appeared and made her kill; the ambiguous ending leaves the door open for a sequel. In some ways, you could say that this same scenario plays out at the end of Libation Bearers – but in reverse. This time, it's Clytemnestra who has been killed, and the murderer is… Orestes, who ends the play by going insane and running away to Delphi, convinced he is pursued by the Furies (spirits of vengeance).
Unlike a modern horror movie, however, the point of Aeschylus's Oresteia probably isn't just to keep churning out as many sequels as possible. Instead, Aeschylus's trilogy is designed to explore some super-important, weighty themes on the nature of revenge and justice. By devoting the first two plays to the theme of revenge – two plays that end inconclusively – Aeschylus is really gunning for the third play, Eumenides, which is about formal, courtroom justice. We can't tell you too much about this right now (you'll have to wait to read Eumenides to get the full picture), but maybe we can get away with a hint or two here. Why do you think Aeschylus would have wanted plays about revenge to be inconclusive? Could this in itself be a commentary on that theme?