We first see Cassandra when Agamemnon rides up to the palace at Argos. Cassandra is in his chariot.
After Clytemnestra convinces Agamemnon to walk on the purple fabrics, into the house, she comes back out to get Cassandra.
Cassandra doesn't answer. Then, the Chorus tells her to listen to Clytemnestra. Cassandra still doesn't answer, nor does she make any move toward the house.
Eventually, Clytemnestra reasons that Cassandra, as a Trojan, must simply not be able to understand the Greek language. Clytemnestra decides not to waste any more time on this matter, so she heads into the house, offstage.
Now the Chorus tries again to convince Cassandra to go inside.
All of a sudden, Cassandra starts speaking – or rather, singing and chanting. The words of her chant are expressions of pure horror. As Collard translates it: "O-o-o-oh! Horror! No! / O Apollo, O Apollo!" (The sound that Collard translates as "O-o-o-oh!" sounds even weirder in Greek: "ototototoi!")
The Chorus asks her what's the matter, but she just keeps chanting about horror and talking about how Apollo has destroyed her.
Eventually, Cassandra asks Apollo what house she has come to.
The Chorus says, "Don't you know, this is the house of the sons of Atreus!"
But Cassandra disagrees; she says that she has come to a slaughterhouse – a slaughterhouse where family members have killed family members.
The Chorus knows what she's talking about, but doesn't go into too many details.
Then Cassandra starts prophesying that Agamemnon will be killed – by his own wife!
The Chorus is very confused and disturbed by this.
Then Cassandra starts saying that she is going to die, too.
The Chorus wavers between understanding exactly what she's saying and pretending not to; they also say that they are helpless to do anything about it.
Finally, Cassandra provides a pretty clear hint that she knows about the murders that took place in the palace – the children of Thyestes whom Atreus (Agamemnon and Menelaus's father) butchered and served to him. She also alludes to the fact that Thyestes slept with Atreus's wife, which provoked the whole thing.
The Chorus tells her she's right; they're amazed that a foreigner could have learned about this story.
Cassandra tells them that she knows because of the prophetic power she was given by the god Apollo.
The Chorus says, "Why did he do that? He must have had a huge crush on you."
Cassandra reveals that this was, in fact the case. But even though she had promised to sleep with Apollo, at the last minute she changed her mind – after he had given her the power of prophecy though.
In revenge for this, however, Cassandra explains, Apollo cursed her. He made it so that, even though she had the power of prophecy, she was condemned to have no one believe her.
The Chorus tells her that they believe her, however. (What do you make of this, Shmoop readers?)
Then, all of a sudden, Cassandra starts having another vision. This one is really spooky. She says that she sees the children of Thyestes nearby, holding their own guts in their hands. Yup.
Cassandra finishes her prophecy by saying that some "bitch" (like, literally, a female dog) is going to kill Agamemnon.
The Chorus doesn't know what to make of this. In fact, they simply tell Cassandra to shut up, on the off chance that her words might bring bad luck against Agamemnon.
When Cassandra persists, they ask her (in Collard's translation), "What man is to bring this evil thing about?" Realizing that the Chorus clearly didn't get the point of the whole "bitch" reference, she just says, "You guys are way off track."
The Chorus tries to press her further, but she just goes off into another prophetic trance.
This time, Cassandra speaks again in metaphorical terms about how Clytemnestra is going to kill Agamemnon – and her too.
She says that this is Apollo's final way of punishing her.
But then, she reflects that someone will come to avenge her and Agamemnon, a child born to kill his own mother.
Finally, comforted by this, and by the fact that the man who captured Troy (Agamemnon) is about to die, she accepts death.
Just before Cassandra heads inside, she stops, repulsed by the smell of blood she claims is coming from inside. The Chorus tries to figure out what's going on, but doesn't succeed. Then Cassandra tells them that she and Agamemnon are going to die; she prays that whoever comes to avenge Agamemnon will avenge her too.
Then, after offering a brief reflection on the fragility of human life, she heads inside.