Still feeling guilty for his mothers murder, and still being pursued by the Erinyes, Orestes takes refuge in Apollos temple at Delphi, who promises to protect him and tells him to appeal to Athena for help. Meanwhile, the ghost of Clytemnestra urges the Furies to continue searching for her son, and they eventually find him.
At that moment, Athena intervenes and decides to settle the whole thing on a judgment, with Apollo acting as Orestess attorney, the Erinyes defending the ghost and Athena and others as the jury. Just as Athena predicted, it results in a tie, after which Orestes is acquitted, something the Erinyes have to accept eventually.
After this play there was originally a Satyr Play called Proteus, but save for a few fragments, it has not survived until today.
Eumenides provides examples of:
- Artistic License Biology: Apollo, argues that women don't really count as kin to their offspring, as they just "nourish the seed" provided by men. This was considered Artistic License by most people even at the time the play was written, so not just a case of Science Marches On.
- Courtroom Episode: Ends the Oresteia trilogy with Orestes being tried in the court of Athens, with gods and furies acting as the defense and prosecution.
- Creator Provincialism: Aeschylus, who lived in Athens and was performing for an Athenian audience, has the final trial take place in Athens after the rest of the trilogy was set in Argos.
- Decided by One Vote: The jury is tied on whether to convict Orestes. In ancient Athens, a tie went to the defendant, so Orestes gets to go free.
- Did You Just Flip Off Cthulhu?: Clytemnestra's ghost berates the Erinyes for sleeping instead of trying to catch Orestes, and even these terrifying beings don't do much more than whimper pathetically and eventually follow her orders.
- Externally Validated Prophecy: Orestes vows, in his gratitude for an Athenian jury acquitting him, that Argos will always have peaceful relations with Athens, and Apollo promises to ensure that Orestes and his descendants will often fight alongside Athens. These are both references to a recent (at the time) treaty between Athens and Argos.
- Female Misogynist: Athena, in her final argument, says she sides with Orestes because she always sides with men over women.
- Greek Chorus: The Eumenides who, in fact, are the same Erinyes of the previous play.
- I Did What I Had to Do: Orestess defense.
- Implied Death Threat: Athena persuades the Furies to back down off of Orestes by pointing out that showing mercy and favouring justice instead of vengeance would lead to them being honored and beloved by the people—oh, and she also has the keys to the storehouse where Zeus keeps his thunderbolts.
- Karma Houdini: Not Orestes, curiously, since he has a BSOD and is being followed by the Erinyes, but rather Electra, who convinced Orestes of doing the killing. Of course, since Orestes was acquitted, you could argue that the acquittal was extended to anyone involved (including Apollo, who was also guilty to a point).
- Kinslaying Is a Special Kind of Evil: The Erinyes believe this, saying that regardless of the circumstances you can't let someone get away with killing their own mother, but they don't have compunctions against other sorts of murders like killing one's husband.
- The Nose Knows: The Erinyes find Orestes following the smell of his mothers blood on his hands.
- Not So Different: The Erinyes point out that, although Apollo claims Zeus cares that people's fathers' deaths don't go unavenged, he himself imprisoned his father in Tartarus. Apollo replies that imprisoning someone, which can be undone, is different than killing.
- Our Ghosts Are Different: Clytemnestras ghost appears more like a collection of dreams or thoughts than a singular being.
- Pet the Dog: Although Apollo could be a real Jerkass in other myths, here he tries to protect Orestes, who honoured his command to kill Clytemnestra.
- Reasonable Authority Figure: Athena, Apollo.
- Slippery Slope Fallacy: The Erinyes argue that if Orestes is given mercy, it will lead to a constant stream of children killing their parents since they know they can get away with it.
- Surprisingly Happy Ending: For the whole trilogy. After two plays of revenge killings, Orestes is forgiven and even the Erinyes back down and take up a life of greater kindness.
- Winged Humanoid: The Erinyes.