The Oresteia recap

After Troy falls, Agamemnon returns to Argos with the captive prophet Cassandra. His wife Clytemnestra, still enraged by his sacrifice of their daughter Iphigenia, kills both of them and rules with Aegisthus. Years later Agamemnon's exiled son Orestes comes home under Apollo's command. Reunited with his sister Electra, he enters the palace in disguise, kills Aegisthus, and then kills Clytemnestra despite wavering before the act. The Furies, divine punishers of familial bloodshed, pursue him. Apollo purifies Orestes and sends him to Athens, where Athena creates a citizen court to judge the conflict between vengeance for a father and guilt for killing a mother. The judges split evenly, and Athena's deciding vote acquits Orestes. She then persuades the furious goddesses to accept an honored role protecting Athens. The family's chain of retaliation ends through public judgment and reconciliation rather than another private killing.

A watchman in Argos sees the beacon announcing that Troy has fallen after ten years of war. Queen Clytemnestra confirms the victory while a chorus of elders recalls the expedition's terrible beginning, when Agamemnon sacrificed his daughter Iphigenia so the Greek fleet could sail. Agamemnon returns in triumph with Cassandra, a Trojan princess and prophet enslaved as his prize. Clytemnestra persuades him to enter the palace over costly fabrics despite his concern that such display is excessive. Cassandra, cursed to speak truths that others reject, foresees both the royal family's history of bloodshed and the deaths awaiting Agamemnon and herself. She enters the palace knowingly. Their cries are heard, and Clytemnestra reveals that she has killed Agamemnon in the bath and murdered Cassandra as well. She presents the act as vengeance for Iphigenia and as justice for other wrongs. Her partner Aegisthus then claims his own revenge for atrocities Agamemnon's father committed against his family. Clytemnestra restrains a final clash with the elders, and she and Aegisthus take control of Argos while Agamemnon's death remains unavenged.

After Clytemnestra and Aegisthus murder Agamemnon and seize Argos, the exiled Orestes returns secretly with his friend Pylades. At Agamemnon's grave he encounters his sister Electra and the enslaved women sent to pour offerings meant to calm the dead. Brother and sister recognize each other, mourn their father, and agree that Orestes must carry out Apollo's order to avenge him. Orestes enters the palace disguised as a traveler and reports his own death. The news draws Aegisthus to meet the supposed messenger without his guards, and Orestes kills him. Clytemnestra then confronts her son. She appeals to their bond and reminds him that she raised him; he hesitates, but Pylades recalls Apollo's command. Orestes kills her beside Aegisthus. He displays evidence of the crime against Agamemnon and tries to justify what he has done, but the Furies become visible to him as avengers of a mother's blood. He flees toward Apollo's sanctuary at Delphi for purification, having avenged one parent by becoming the killer of the other.

Orestes reaches Delphi after killing Clytemnestra to avenge Agamemnon. Apollo purifies him and directs him to seek Athena's judgment, while the ghost of Clytemnestra urges the Furies to continue their pursuit. Orestes takes refuge at Athena's image in Athens. When Athena arrives, she hears the Furies' charge that a son's murder of his mother demands punishment and Orestes' answer that Apollo ordered the act in response to his father's murder. Athena creates a court of Athenian citizens to decide the case, with the Furies prosecuting and Apollo defending Orestes. The judges divide evenly. Athena casts her vote for acquittal, freeing Orestes to return to Argos and ending the immediate chain of vengeance. The defeated Furies threaten Athens, but Athena patiently offers them a permanent place of honor and the power to bring prosperity and uphold justice. They accept, exchange curses for blessings, and become the Eumenides, the Kindly Ones. A civic procession leads them to their sanctuary, closing the trilogy with blood feud replaced by trial and with the old divine powers incorporated into a new public order.

At Orestes' trial in Athens, the citizen judges divide evenly over whether he must be punished for killing Clytemnestra. Athena's vote breaks the tie in favor of acquittal, ending the Furies' legal claim against him and allowing him to return to Argos. The Furies react with anger and threaten the land, but Athena does not drive them away. She offers them an honored place beneath Athens and a continuing power to bless fertility, protect justice, and punish destructive conduct. They accept the settlement, becoming the Eumenides, or Kindly Ones. An Athenian procession escorts the transformed goddesses to their new sanctuary. Orestes is freed, Apollo's command is vindicated in the immediate case, and the cycle of private revenge within the house of Atreus gives way to a civic system in which disputed blood guilt is judged by a court and formerly hostile powers are incorporated into the city's order.