Perseus was the son of Danae and Zeus. Danaes father heard about his birth, and in fear of Perseus killing him, he threw Perseus and his mother into a chest and into the sea. From there, if they were killed, Zeus would have to put the blame on Poseidon.
Somehow, from way up on Mt. Olympus, Zeus steered the chest onto the shore of an island. A fisherman found them. Danae told him her story, and he took them in like he was their father.
Perseus grew into a strong and proud youth. The king of the island wanted Danae for his queen, but since she was a bride of Zeus, she turned him down. Perseus protected her from the king. This made the king want to get rid of him.
He devised a plan. He told the kingdom he was to wed a princess from another island. Men brought gifts to the king, as was the custom. Unfortunately, Perseus was poor, and he offered his service to the him. The king told him to slay Medusa, and thought Perseus would die trying. You see, all who looked at her would turn to stone- thats how ugly she was.
Perseus excepted the request, and went out searching for the Gorgon Island, but he couldnt find it. Athena and Hermes saw Perseus wandering around, and went to help him. They both gave Perseus an item that was needed to defeat Medusa. Athena gave him her shield that was polished like a mirror, and Hermes gave him his sword. But, he also needed three other things that he could only get from the Nymphs of the North. There was only one problem: neither of the two gods knew exactly how to find the Northern Nymphs.
So, instead, Hermes took him to the Fates. They were three old goddesses, and they shared one eye between them. When Perseus reached where they were, he stole their eye, and in ransom, he received directions. He gave them back their eye, and left- it was easy as that!
Perseus eventually made it to the Nymphs of the North, and he did get the three crucial items. They were: sandals that could enable the wearer to fly, a bag that could hold anything, and a cap that made him invisible. He was ready.
When he arrived at the island, he looked into Athenas shield, and not down. He found them all sunbathing on the shore, asleep. Snakes grew on their heads, and around them, he saw stones that once had been men. In one easy step, he flew down to the sisters, and cut off Medusas head.
Just then, the other sisters woke up, but could not see him. He had put on the cap. He put Medusas head into the bag, and flew away.
On his way home, he flew over a coast, Ethiopia, and saw a girl chained to a rock. As she saw him coming, she warned him to fly away, "or he would be eaten by the sea monster". Perseus said that if he saved her, who was Andromeda, she would wed him.
Right then, the sea monster rose from the water ready to kill. Perseus dug his sword deep into the monsters neck, and it died. The blood from it, though, tinted the water red, and it is now known as the Red Sea.
When he arrived home, he arrived to an empty house. Danae and the fisherman had hidden, because as soon as Perseus had left, the king had tried to carry her off. Perseus went to the kings palace, and took everyone by surprise. He said, "I give you, your requested head!" The king and his soldiers looked at the head and was turned to stone.
Then, Danae and the fisherman came out of hiding, and they made the fisherman the new king. Perseus and Andromeda were married.
Perseus gave the Gorgon head to Athena, because he thought it was too dangerous for mortals. She returned the other items he had borrowed. And it turned out to be a "happily ever after" sort of deal.