In case you have forgotten everything from yesterday (it was a long time ago, I know), I shall provide a brief recap. (Or you can go read Part I in its entirety.)
King Acrisius was told by the Oracle that his grandson (Perseus) would kill him. So Acrisius put his daughter Danae and her baby son Perseus (who also happened to be the son of Zeus) in a chest and tossed them in the sea hoping they’d drown. They ended up in King Polydectes’ realm. After Perseus grew up Polydectes decided he wanted to marry Danae. She said Eww. And in defense of his mother, Perseus said he’d get Polydectes anything he wanted. Polydectes sent Perseus off to get the head of Medusa (and hopefully die).
If you’ve seen Clash of the Titans, it might have something to do with this story (so My Friend the Internet tells me), but as I haven’t seen the movie I can’t comment. Well, I can’t comment accurately.
So there was Perseus, wandering around, not having a clue where he was going and feeling generally down about Life when poof! Athena and Hermes just happen to show up. Sibling relationships among gods and demigods are never straightforward but in this case they offered to help Perseus. Hermes lent Perseus his winged sandals and Athena lent him her shield. They also gave him directions on how to find Medusa and how to kill her. All of which was very useful.
Perseus said Thank You very nicely because his mother had taught him well and it’s never a good idea to annoy the gods even if you are siblings.
Eventually Perseus got to Medusa’s digs (I’m leaving out the long, complicated bits—you’re welcome) and he lopped of Medusa’s head and then dumped it into a magic bag. After which he had a bunch of adventures (I’m leaving most of them out—you’re welcome).
On his way home, however, he saw a Beautiful Maiden chained to a rock. It was Andromeda (remember her? She was chained to a rock because of a different oracle and her vain momma, Cassiopeia). Perseus fell in love, freed her from her chains (turned an annoying sea monster into stone using Medusa’s head), and married Andromeda.
They stopped at a lovely island so Perseus could compete in the Games (think American Ninja Warriors but with togas, races, and throwing things). Perseus did very well except when he threw the discus it hit an old man who died. News flash: the old man was his grandpa, King Acrisius, who was trying to avoid the death the oracle had predicted. Did I mention you can’t outsmart an oracle?
Then Perseus and Andromeda went home so Andromeda could meet her new Mom-in-Law and they found out that King Polydectes was still saying “marry me” and Danae was still saying “no way” and Polydectes hadn’t really read up on How to Treat Women. This Pissed Off Perseus in a big way.
Being a Good Boy, Perseus hiked up to the castle, told his friends to shut their eyes, pulled Medusa’s head out turning everyone else into stone, and took his mom off to meet his bride and live happily ever after. Until they died and got put in the sky as stars.
And that is exactly what happened.