The play opens with Pythia, the priestess of Apollo, preparing to perform her morning prayer. Her ritual is interrupted, however, by a bloodstained refugee who has come to her temple to be cleansed. It is Orestes, the son of Agamemnon and Clytemnestra, who killed his mother in order to avenge her murder of his father. Following him is a relentless band of Furies, demonic goddesses whose only aim in life is to punish human wrongdoers.
Though Pythia is terrified by this sight, and flees immediately, the god Apollo himself takes her place. He reveals that Orestes only killed Clytemnestra at his divine command, and explains to the audience that he has lulled the Furies to sleep, before expressing his hatred of the merciless goddesses. Apollo tells Orestes that he must continue to Athens, where Athena, the goddess of wisdom, will try his case. In the meantime, however, he offers his half-brother, the god Hermes, to guide Orestes to Athens.
After Orestes has exited, the ghost of Clytemnestra appears, scornfully cursing the Furies for their laziness. They wake up and are horrified to find their prey has escaped, cursing the Olympian gods for helping a guilty man defy their power. At this moment, Apollo emerges from the temple, and a verbal fight begins. Apollo finds the Furies contemptible and horrific, relics of a time when vengeance was more important than justice. The Furies, meanwhile, believe that Apollo is trying to steal their power. The dialogue ends with the Furies vowing to pursue Orestes, even as Apollo promises to protect him.
The scene shifts to Athens, where Orestes prays to Athena just as the Furies find him once again, threatening and tormenting him when they do. Soon after, Athena herself enters, and commands both the Furies and Orestes to tell her who they are and why they’ve come to Athens—she explains that she must protect her city at all costs. Both sides explain their presence to her, and agree to abide by her ruling.
Athena wishes to serve justice, but fears the wrath of the Furies. She decides, however, to create the first ever murder trial in order to determine Orestes’ guilt, recruiting ten honorable citizens to form a jury. The trial begins, with the Furies arguing that Clytemnestra’s life was worth as much as Agamemnon’s. Apollo, however, argues that men’s lives are worth more than women’s, and Athena agrees, casting the deciding vote that allows Orestes to go free, an innocent man.
This chain of events horrifies the Furies, who believe that Athena has stolen their power from them. Athena, however, wisely offers the Furies a new role: patron goddesses of Athens. She explains that if they provide the city with peace and prosperity, they will receive offerings and prayer in return. After some convincing, the Furies agree, and take on the mantle of the Eumenides—“the kindly ones.”