A Crisiua, King of Argos, had only one child, a daughter named Danae. He wanted a son and asked an oracle what the future held the oracle replied "You will have no son, and your grandson will kill you." The terrified king locked his daughter away in a high tower behind doors of brass.  However, the god Zeus came to her in a shower of gold, and in time, she bore a son Perseus.

Fearing Zeus's wrath if he killed his daughter and grandson, Acrisius cast Danae and Perseus adrift on the sea in a wooden chest. Danae prayed to Zeus for help and, instead of being swamped by the waves, their chest washed up on the island of Seriphos.

At length, the island's King, Polydectes, met Danae. He desired to marry her, but she refused him.  With Perseus, who was by now fully grown, to protect her , the king knew he would never bend her to his will.  He decided to get rid of Perseus.  He held a banquet for the island's young men.  All the guests brought gifts, except Perseus, who was too poor. Ashamed, he promised the king a present.  "Bring me the head of the Gorgon Medusa," Polydectes sniggered.  Medusa was a terrible monster, with snakes for her hair and a glance that turned people to stone.  The task was impossible.

Zeus took pity on Perseus and sent two Immortals, Athene and Hermes, to him.  Athena lent Perseus her shield, saying: "Look only on Medusa's reflection in the shield and her stare will not harm you."  Hermes lent Perseus a sickle to cut off the Gorgon's head.  He also told Perseus how to find the Nymphs of the North Wind, who would lend him winged sandals and a wallet to hold Medusa's head, and fetch for him the Cap of Invisibility from Hades, god of the Underworld.

Wearing sandals and cap, Perseus flew unseen to the far west. He found Medusa and her two sisters asleep among the weather worn statues of other heroes, all turned to stone by her glance.  Looking only at Medus's reflection in his shield, Perseus saw a girl chained to a rock.  Her name was Andromeda, and she was about to be sacrificed to a sea monster to stop it from laying waste to her father's kingdom.  As the creature rose from the deep, Perseus pulled out Medusa's head and turned the monster to stone.  Perseus and Andromeda, who had fallen in love at first sight, were married soon after.

By the time Perseus returned to Serphos, Polydectes had made Danae a slave.  The kind was amazed to see Perseus alive and did not believe he could have killed Medusa.  Perseus showed him the Gorgon's head---and he was turned to stone where he stood.

As for the oracle's prophecy, it did come true.  Perseus did eventuall kill his grandfather.  He was throwing a discus one day when, by the will of the gods, it hit Acrisius. The winged horse Pegasus, became the steed of another hero, Bellerophon.  He rode the horse in his fight against the fire breathing Chimaera, a monster with a lion's head a goats' body, and a serpents tail.  Bellerophon killed the creature by thrusting his spear into its throat.   The spear had a lump of lead on the end, which the Chimaera's hot breath melted, searing its insides.

Bellerphon was such a great man that he came to think himself the equal of the gods. He rode Pegasus right up to Olympus, but Zeus sent a gadfly to sting the horse, which shied.  Bellerophon was flung to earth and ended his days a beggar.  As for Pegasus, Zeus used the creature to carry his thunderbolts.