An Oracle tells King Acrisius that his grandson will kill him so he locks his daughter in a cell so she doesn't have any children. But Zeus comes to the cell and Danae, the daughter, carries Zeus's child.
I'm going to be locked in here forever!!!
King Acrisius throws Danae and her son, Perseus into the sea, but they survive and end up in another kingdom.
King Polydectes wants to marry Danae but he hate Perseus. So he sends Perseus, Danae's son, on an impossible mission to fetch Medusa's head so that he will die.
It's time for you to go on an adventure Perseus. Kill Medusa then bring her head here.
Perseus travels away and finally finds Medusa sleeping along. Instead of looking right at her eyes he looks into his shields reflection and to chops off Medusa's head. On a cliff Perseus saw a beautiful maiden named Andromeda and saved her from the sea serpent.
Kyahh!! Help me!!
Perseus claims that he killed Medusa, but Polydectes doesn't believe him. Perseus gets angry so he shows Polydectes Medusa's head and turns him into stone.
You never killed her!!
I killed her!!
Perseus goes back to King Acrisius' kingdom along with Danae and Andromeda and fulfills the Oracle by killing his grandfather.