Even though Agamemnon gets a shout-out in the play's title, Clytemnestra may well be its most interesting character. By interesting, we don't mean likable – after all, technically speaking, she is a liar, a two-timer, and a murderer. But maybe that's just part of her charm. We'd better explain. The first thing we learn about Clytemnestra is from the Watchman in the opening scene of the play. He isn't her biggest fan, though he doesn't give us any explanation why. Instead, he makes a vague remark about how the household "is not managed for the best as it was before" (19). But what does that mean, exactly? Did Clytemnestra stiff him on his overtime pay or something?
We might get a hint of what the Watchman means later on in the play, when the Chorus tells the Herald that Clytemnestra's public statements about how much she loves her husband aren't exactly honest. Does the Chorus say this because it knows about her affair with Aegisthus? We aren't told. If this was common knowledge in Argos, it is possible that this is what the Watchman is referring to – though, it isn't clear how Clytemnestra's extra-marital love life would necessarily make her a bad manager of the household.
So, yes, Clytemnestra is having an affair while Agamemnon is off fighting at Troy. Ten years might seem like a long time to wait for one's husband; of course, Penelope, the heroine of Homer's Odyssey waited twenty years for her husband to come back. Everyone thinks she's exceptional, though. But what about the fact that Agamemnon had his daughter Iphigenia sacrificed on the way to Troy, just to get the goddess Artemis to send the fleet some favorable winds? We can see how that might have made Clytemnestra think a little less of her husband, and maybe this is why she turned elsewhere for romance.
When he shows up at the end of the play, however, Aegisthus seems like a bit of a dweeb. Does this just mean Clytemnestra has bad taste in men? Or do you think Clytemnestra deliberately sought out Aegisthus knowing he held a grudge against Agamemnon because of the crime of Agamemnon's father Atreus? If so, that would mean she had been planning revenge against Agamemnon for a long time and was just looking for an accomplice. Unfortunately, the play doesn't give us any firm information about these matters.
What the play does show us is that Clytemnestra is one accomplished conspirator and murderer. First of all, there is the deception she carries off, by playing the role of loving wife in front of the Herald, the Chorus, and Agamemnon when he shows up. Even though the Chorus tells the Herald not to believe every word she says, it's pretty clear they don't suspect Clytemnestra of being a murderer. The proof of this comes in the Chorus members' reaction to Cassandra's prophecies, when they go way off track by assuming she is referring to a man who will kill Agamemnon. Frankly, though, who can blame them? We don't think anybody could have predicted the truly psychotic scene when Clytemnestra reveals herself standing over the bodies of Agamemnon and Cassandra, and ecstatically describes how Agamemnon's blood landed on her like rain on a farmer's field. Yikes.
We see some more of Clytemnestra's psychotic side in the debate with the Chorus that follows, but at the very end of the play she has calmed down and taken on a different role. First, she prevents Aegisthus from fighting the Chorus; then, she leads him inside and tells him that they will be joint rulers in Argos. Joint rulers? Who is she kidding? With her air of confident authority, it's hard to doubt that Clytemnestra will be wearing the crown in their relationship.