by Aeschylus
[in summation + spoiler alert(!)]
So, in a move not in this play but “familiar to Greek audiences,” Agamemnon kills his daughter to beg Artemis, who is punishing him for boasting, to let his ships move forward on their way to Troy.
At the start of this trilogy, Agamemnon returns from the Trojan War a hero, and is subsequently and almost immediately murdered by his wife, Clytemnestra, who’s upset about their daughter and also sleeping with someone else. (While kill-crazy, she also inexplicably murders Cassandra, a seer. It’s not entirely clear how her daughter’s death justifies that decision (i.e. not clear to me, non-Greek audience).)
In part two, Clytemnestra’s exiled son, the eponymous Orestes, shows up and kills her and her lover to avenge his father, which, according to Apollo, is the only appropriate action. Apollo’s claim (in part three) is basically that the father is the true parent, the mother is just incidental. In fact, you may remember that Athena was born solely of Zeus, so, quite opposite to Christian tradition (from virgin birth to Strindberg’s The Father), it is the mother that is *unnecessary* for the Greeks. (Side note: Cassandra’s death doesn’t seem to be of concern to anyone anymore.)
Thanks to Apollo’s advice, in the last of the trilogy, Orestes is doomed to be pursued by the furies–because matricide is far worse than killing your husband (not a blood relative). Killing your baby to sacrifice to a god is apparently okay too, though bragging to Artemis about anything is decidedly not okay. There is a trial, an unexpected happy ending, and a hint at the hope that mercy and fairness will become a trait of the heretofore unpredictably whimsical Greek gods.
from Wikipedia: “The Oresteia was originally performed at the Dionysia festival in Athens in 458 BC, where it won first prize. Overall, this trilogy emblemizes the shift from a monarchal system of vendetta in Argos to a democratic system of litigation in Athens.”