Some time after Agamemnons murder, his son Orestes and a friend, Pylades, arrive at his grave after a long exile. Soon, they both hide as Orestes sister, Electra, arrives at the tomb with some slaves carrying libations. She sees two locks of hair in the tomb, left there by Orestes earlier, prompting him to come out of his hiding place and convince his sister of his identity.
She tells him of Aegisthus and Clytemnestras plot to murder Agamemnon and, after a long rant that involves summoning the spirit of their father to help them, Orestes decides to avenge his father by murdering both his mother and her lover.
Orestes and Pylades pretend to be wandering travelers and knock on the door, calling on Aegisthus with news of Orestes death. Clytemnestra, delighted, goes inside to call Aegisthus, only for him to die when he meets Orestes in private. When she finds out, he threatens to kill her too, in spite of her pleading and reminding him of the fact that she bore and raised him. Orestes has trouble deciding if he has to murder her too to avenge his father or not, but eventually decides the cause is just and does it. Then he wraps both corpses on Agamemnons cloak.
Sadly for Orestes, the cycle of violence doesnt end there. Anyone in ancient Greece who slays a family member has broken a serious moral law and becomes the rightful prey of the Erinyes or Eumenides ("Kindly Ones"), aka the Furies, incarnations of vengeance whom even the gods cannot control. The story continues in Eumenides...
The Libation Bearers provides examples of:
- 0% Approval Rating: None of the slaves and other people in the household are big fans of the current ruler, on account of them murdering Agamemnon.
- Abusive Parents: Electra and Orestes see Clytemnestra as this. Electra describes how her mother treats her little better than a slave, and Orestes is furious about being sent away and essentially exiled to give Clytemnestra the opportunity to kill Agamemnon.
- After-Action Villain Analysis: Orestes delivers a speech at the end about Clytemnestra and Aegisthus, why he thinks they were horrible, and what led them to acting as they did.
- Big Bad Duumvirate: Clytemnestra and Aegisthus.
- Big Damn Reunion: Orestes and Electra are reunited after being separated for years at the. beginning of the play.
- BrotherSister Team: Orestes and Electra, teaming up to avenge their father by killing Aegisthus and Clytemnestra.
- Bystander Syndrome: The chorus reaction to Aegisthus murder.
- Cycle of Revenge: Picks it up from the previous play and leaves it open for conclusion.
- Dreaming of Things to Come: Clytemnestra dreams of giving birth to a snake and giving it the breast while it also sucks her blood. She understands it shortly before her death.
- Downer Ending: Orestes kills both Aegisthus and Clytemnestra, but not only does the Cycle of Revenge not end there, but he also is tormented by the Erinyes.
- Evil Matriarch: Clytemnestra.
- The Exile: Orestes.
- Faking the Dead: Orestes, dressed as a guest, tells Clytemnestra that Orestes is dead.
- Foreshadowing: The characters keep mentioning the Erinyes throughout the play, and they finally appear after Orestes has consummated both murders. Also, another that goes back to the previous tragedy, when Cassandra warns that Orestes will kill Aegisthus.
- God Save Us from the Queen!: Clytemnestra killed her husband, the king Agamemnon, and now Orestes plans to kill her in revenge.
- Greek Chorus: Slave women.
- Heroic BSoD: Orestes suffers this after his mothers death.
- Killed Offscreen: Aegisthus and Clytemnestra (given this was an Ancient Greek play, they couldn't do the violence on screen.
- King Incognito: Orestes gets into the palace by pretending to be a foreign guest.
- I Did What I Had to Do: Orestes convinces himself that he must kill his mother to avenge his father.
- Libation for the Dead: It's actually in the title.
- Made a Slave: The chorus describes being made slaves after their cities were taken.
- Matricide: This is, actually, one of the few examples of matricide in fiction.
- My God, What Have I Done?: What Orestes feels afterwards.
- Noble Bird of Prey: Orestes compares Agamemnon to a powerful eagle and him and Electra to the eagle's young.
- Rightful King Returns: Orestes, Agamemnon's heir, returns to kill Aegisthus and Clytemnestra and take over rulership of Argos again - though the latter part gets delayed courtesy of the Erinyes.
- Ruling Couple: Clytemnestra and Aegisthus.
- Sacred Hospitality: Orestes and Pylades use this as an excuse to be received when they disguise themselves as travelers.
- Sound-Only Death: Aegisthus (as typical for Greek tragedies where they couldn't show the violence on screen).
- Stay in the Kitchen: The chorus gives a speech about various women who committed evil deeds and conclude by saying they honor women who stay in their homes and do nothing.
- Together in Death: Orestes threatens to kill Clytemnestra right after killing Aegisthus, saying that because they chose to live together and love each other (instead of Clytemnestra staying with Agamemnon) they should die together. He makes good on his oath.
- Undignified Death: Electra and Orestes see Agamemnon's death as this (being tied up in a bath and killed by his wife while he was helpless), and mention how undignified it is while trying to talk to his ghost, in order to anger him enough that he will help them in their revenge.
- Villains Want Mercy: Clytemnestra tries to convince Orestes to spare her life. It doesn't work.
- Winged Humanoid: The Erinyes.
- You Killed My Father: Orestes's motivation for murdering both his mother and Aegisthus is their actions in the prior play.