King Acrisios was told that his daughter would have a son that would later on kill him. He locked his daughter and her son in a brass chest and sent them out to fee to try and avoid his fate.
Dictys and Polydectes rescue Danae and her son, Perseus. They live on the island for some time, and Perseus grows up. Perseus then says that he owes Polydectes his life, and Polydectes sends him to retrieve Medusa's head as a way of paying him back.
Perseus aquires gear from Athene and Hermes, and sets of to find the Gorgon. He approaches the cave and sees that the three Gorgons are asleep.
Perseus uses his shield to look at Medusa, and he cuts off her head with his sword. He then puts the head in his knapsack and heads back to Polydectes.