The king was told that his future grandson was going to kill him. The only way to prevent this was to imprison his daughter, Danae.
Zeus discovers Danae and falls in love with her and they have a son named Perseus.
The king puts Danae and Perseus on a box and throws them in the ocean. They are later found by a fisherman on an island.
King Polydectes tricks Perseus saying that his great gift needs to be Medusa's head. Perseus agrees and receives help from the gods. Perseus receives a shield, a helmet, and winged shoes to conquer Medusa.
After Perseus conquers Medusa, he saves Princess Andromeda who was chained to a rock.
Perseus returns to King Polydectes who has punished Danae in his absence. Perseus shows Medusa's head, and the king and all his men turn to stone. Everyone lives happily ever after.