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:
- 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 Erinyes.
- Evil Matriarch: Clytemnestra.
- 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.
- Greek Chorus: Slave women.
- Heroic BSoD: Orestes suffers this after his mothers death.
- 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.
- My God, What Have I Done?: What he feels afterwards.
- Patricide: This is, actually, one of the few examples of matricide in fiction.
- Sacred Hospitality: Orestes and Pylades use this as an excuse to be received when they disguise themselves as travelers.
- Winged Humanoid: The Erinyes.
- You Killed My Father: Orestes' motivation for murdering both his mother and Aegisthus is their actions in the prior play.