King Acrisius of Argos has a stunningly beautiful daughter but wants a son, so he prays to the gods. Apollo tells him not only that Acrisius will never have a son, but also that the son of his daughter will kill him.
The only way to fully prevent this prophecy would be to kill his daughter, Danae, but Acrisius fears what the gods would do to him. Instead, he imprisons Danae in a bronze house without a roof and guards her carefully.
Arcisius does not expect, however, that Zeus will come to her and impregnate her.
Perseus is born, and after Acrisius discovers the baby, he puts Perseus and Danae in a box and sets it out in the ocean. Luckily (or thanks to Zeus), the box washes up on a small island, where a kind fisherman named Dictys takes Danae and Perseus.
They live happily until Dictys's brother, King Polydectes, falls in love with Danae and decides to get rid of her son. Polydectes convinces Perseus to kill the Medusa, a horrifying beast with snakes for hair. But this feat seems impossible because whoever looks at the snakes will turn instantly to stone.
Hermes gives Perseus guidance and a sword stronger than the Medusa's scales. He tells Perseus that to fight the Medusa Perseus will need special equipment from the Nymphs of the North.