The Murder of Agamemnon
There are differing accounts of Agamemnon's murder. The most famous version, that depicted in Aeschylus's play Agamemnon, involves the unlucky king being entangled in a net or gown and stabbed to death in his bath. In The Odyssey, however, Homer tells a different story: Aegisthus sets watchmen along the coast to bring news of Agamemnon's return, then he lures the king to a banquet in his honor, and murders him, his companions, and Cassandra there.
It's interesting to note how in Homer, the earliest extant source, Clytemnestra has little or nothing to do with the murder. She's a passive player, seduced and easily led by Aegisthus, whereas in Aeschylus, she's the principal actor. Homer also glosses over her murder at the hands of Orestes, and says nothing about Orestes' subsequent madness; the implication is that he kills her along with Aegisthus, holds a funeral feast, and that's the end of the matter.
So which version is the truer one? Agamemnon was locked in a bitter blood feud with Aegisthus, so it seems unlikely he would have accepted the man's hospitality.
It's interesting to note that Homer doesn't mention the sacrifice of Iphigenia, either, thereby removing Clytemnestra's motivation for the murder. In The Iliad, Agamemnon offers Achilles one of his daughters in marriage, and lists them thus: Chrysothemis, Laodike (Elektra?) and Iphianassa (Iphigenia?). There is a hint of marital discord when Agamemnon states that he prefers Chryseis to Clytemnestra, but in The Odyssey, she is described as a good-natured woman who wanted nothing to do with Aegisthus at first. That's about as much Atreid family scandal as Homer ever provides.
Bear in mind that Homer was an Ionian Greek, whose audience might have included descendants of the Atreid dynasty. They would not have wanted to hear about the crimes of their ancestors.
Aeschylus's Athenian audience certainly would have known the story before they even entered the theater. Of course, they knew their Homer, but it seems there was another, bloodier, and more salacious version of events out there. Greek playwrights took preexisting stories and reworked them, just as Shakespeare did some 1,900 years later.
I suspect the Aeschylus story is closer to the truth, insofar as we can say that these events really took place. Just look at the frescoes from the Mycenaean palaces. Women are everywhere, as priestesses and princesses. A queen like Clytemnestra would have been a formidable individual. As mistress of the citadel, she would have been perfectly capable of taking a lover, and installing him in her household. And as high priestess, she would have been more than able to personally carry out the murder of her husband like the killing of a sacrificial animal.