The poor princess is said, in the Byzantine world of Greek myth, to have been both blessed and cursed by Apollo. The god gave her the gift of prophecy, but then, because she refused to become his lover, he ruled that no one would ever believe a word she said.
When her brother Paris was born, Cassandra warned that he would bring ruin to Troy. Kill him, she said (life was cheap in 1200 bc), but no one listened.
When Paris set out to claim Helen, the most beautiful woman in the world, as his mistress (the one he won in that golden apple contest), she urged him not to go. But he didn't listen.
When he returned with his gorgeous Greek trophy, his sister tore out her own hair, confirming her reputation for being mentally unhinged.
Helen was welcomed by the Trojans, despite the fact that Menelaus, her rather angry husband, had launched 1,000 warships to get her back. For nine years, Troy was besieged by the Greeks. Heroes such as Hector, Achilles and Paris died in the hot sand that surrounded the city.
Then the Greek Odysseus had an idea. "Let's pretend we've had enough," he told his captains. "Let's strike camp and set sail for home, but we'll leave the Trojans a farewell gift. We'll leave them a wooden horse."
And so, one morning Cassandra sees the great wooden horse at the gates of her city and hears the debate about whether to bring it into Troy.
"Don't do it," she cried. "There are soldiers hidden inside it. It is a trick."
No one listens. To her relief, someone else speaks up on her side. It is another seer - one who's not cursed by Apollo. Laocoon agrees with his princess and utters those immortal words: "I fear Greeks, even when bearing gifts ..."
But still no one listens. The Trojans open the gates and the rest, as they say, is history.