summarized by John P. Pratt
The following is a conglomerate from Edith Hamilton (Apollodorus), Graves, and others. Parts found in only one account, of doubtful authenticity are in brackets.
There were two twin brothers Proteus and Acrisius who took turns ruling a kingdom until Proteus lay with Acrisius's sister after which Proteus fled. Proteus married Anteia. There was a war and they divided the kingdom: Acrisius got Argos, Proteus got Tiryns. Seven giant cyclops fortified Tiryns with massive walls.
When Acrisius discovered Perseus, Danae told him that Zeus was his father. He did not believe her, but he was afraid to kill them for fear of the gods, so he locked them in a wooden ark and launched them into the sea. They were washed up on a island named Seriphos among many islands. A kind fisherman named Dictys ("net") found the chest, opened it and found them still alive. He and his kind wife had no children and took them home and cared for both of them for many years, until Perseus was grown.
Dictys' brother, Polydectes, was the local king, who fell in love with the still very beautiful Danae. Perseus, now grown, was a formidable defender of his mother against Polydectes. So Polydectes sought a plan to get rid of Perseus. He pretended to be in love with Hipposdameia, daughter of Pelops, and called his subjects together to announce their marriage. He asked each to give him gift of a horse, and all did so, except Perseus, who had no horse. Perseus announced that declared he would bring back a better gift than anyone else. This is what Polydectes wanted, so he asked Perseus to bring back the head of Medusa as a gift.
The Medusa was one of the three Gorgon sisters. They were monsters who lived on an island, who were known far and wide because of their deadly power. They had tusks like boars, protruding tongue, thick dragon scales, hands of brass, wings of gold, and a face so ugly that all who looked at it were turned to stone. Medusa was distinguishable from the others because she had snakes for hair. Medusa had been beautiful in her youth, especially her hair, but had lain with Poseidon in the temple of Athene. For punishment, Athene had cursed Medusa to look as she does. She was the daughter of Phorcys who had offended Athene by leading the Libyans of Lake Tritonis in battle.
Perseus left on a ship, without telling his mother where he was going, and sailed to Greece to find out where the Gorgons lived. The priestess at Delphi told him to seek the land where they eat only acorns. He went to Dodona, the land of talking oak trees which declare Zeus's will and where the Selli lived who made bread of acorns. They did not know where the Gorgons lived, but told him he was under the protection of the gods.
As he continued, he met a man carrying a wand of gold with wings at one end, wearing a winged hat and winged sandals. It was Hermes, messenger of the gods. Hermes told him he must be properly equipped to fight Medusa, and what he needed was in the possession of the Nymphs of the North (Stygian Nymphs). Their locations was known only to the Gray Women, [who were the sisters of the Gorgons]. These women dwelt in a land where all was dim and shrouded in twilight. No ray of sun looked ever on that country, nor the moon by night. They were very old and withered, and had only one eye [and one tooth] between the three of them. It was their custom to take turns with it: when one was done using it, she would remove it from her forehead and hand it to another.
All this Hermes told Perseus, and then unfolded his plan. [Because the Gray women were the sisters of the Gorgons, he would have to trick them.] He must keep hidden until he saw one of them remove the eye from her forehead. Then he must rush foreward and take the eye and refuse to return it until they told him how to find the Nymphs of the North.
Hermes then presented him with a sword made of diamond (adamant) made by Hephaestus, which could not be broken by Medusa's scales. Athena then appeared and gave him her breastplate of polished bronze which he carried on his left arm, and the sword in his right. She told him to look at Medusa only in its reflection, to avoid being turned to stone.
Hermes then guided Perseus on a long journey across the ocean to the foot of Mount Atlas where the Gray sisters acted as lookouts. He found the Gray Women sitting in their thrones, in the dim light looking like gray swans. They had the form of swans, but human heads, and under their wings they had arms and hands. Perseus executed the plan exactly. When he snatched the eye [and the tooth] it was a moment before the three realized they had lost it, for each thought the other had it. But Perseus told them he had it, and they [reluctantly] told him the location of the Nymphs of the North. Then he gave them back the eye. [He kept the eye and tooth to keep them from warning their Gorgon sisters of his approach.]
He and Hermes then left for the Land of Hyperboria, the land beyond the North Wind. It is said of that land, "Neither by ship nor yet by land shall one find the wonderous road to the gathering place of the Hyperboreans." But Perseus had Hermes with him, so the road lay open. He found a host of happy people who are always banqueting and joyous. They showed him great kindness and welcomed him to their feast, and the maidens dancing to flute and lyre paused to get him the gifts he sought. These were a) winged sandals enabling him to fly, b) a magic silver pouch that would adjust itself to the size of whatever it held, and c) a cap or helmet of darkness from Hades which made the wearer invisible. Hermes knew where the Gorgons lived, so the two flew back across the Ocean and over the sea to the Terrible Sisters' Island.
The Gorgons were all three asleep when Perseus found them. In the mirror he could see them clearly: they had great wings, bodies covered with golden scales, and hair a mass of twisted snakes. Athene now appeared beside him and told him which one was the Medusa. The other two, Stheno and Euryale, were immortal. Perseus looked at them in the shield, and Athena guided his hand as he cut off her head. To his surprise the winged horse Pegasus and the warrior Chrysaor grasping a golden curved sword sprang full grown from her dead body. Perseus was unaware that these had been begotten on Medusa by Poseidon in the temple of Athene. He decided not to antagonize them and dropped her head into the pouch. The other two sisters were awakened by their new nephew, but could not find him because of his cap of invisibility. He escaped southward and Hermes left him.
Strong winds blew him across the sky like a raincloud, so he stopped to rest near the palace of the Titan Atlas, who refused him hospitality. As a punishment, Perseus showed the Gorgon's head to Atlas and turned him into a range of mountains that now bear his name. The next day he flew across the Libyan desert and some drops of the Medusa's blood fell on the sand and bred a swarm of poisonous snakes, one of which later killed Mopsus the Argonaut. [He dropped the eye and tooth into Lake Tritonis.]
As he rounded the coast of Philistia (Palestine) he caught sight of Andromeda, who was chained to a cliff on the seashore. She was the daughter of Cepheus, the Ethiopian King of Joppa (Tel-Aviv, nearest port to Jerusalem), and his wife Casseiopeia. Casseiopeia had boasted that both she and her daughter were more beautiful that the Nereids, some very beautiful sea nymphs. They complained to Poseidon who sent a flood and a sea monster to devastate the coast near Joppa (the Gaza Strip). When Cepheus consulted the Oracle of Ammon he was told that his only hope of deliverance was to sacrifice his daughter Andromeda to the sea monster. His subjects chained her to a cliff, wearing certain jewels, and left her to be devoured.
As Perseus flew over, he at first almost mistook her for a marble statue. Only the wind ruffling her hair and the warm tears on her cheeks showed that she was human. Perseus instantly fell in love with Andromeda. As Perseus flew to her and asked her why she was chained there. Shy Andromeda, totally different from her vainglorious mother, at first did not answer. Finally, she told Perseus her story, but broke off with a scream as she saw the monster approaching.
Perseus saw Cepheus and Cassiopeia watching anxiously nearby and quickly went to consult with them. They agreed that if he rescued her, she should be his wife and Cepheus offered him his kingdom as a dowry. They also agreed to let Perseus take her back to his home at Seriphos. He took to the air, grasped his sword, and diving murderously from above, beheaded the approaching monster, which was deceived by his shadow on the sea. He had drawn the Medusa's head from the pouch in case the monster had looked up. The headless body of the monster dropped back into the water. He laid Medusa's head face down on some seaweed, which turned instantly to coral. He then cleansed his hand of blood and made three altars, on which he sacrificed a calf, a cow, and a bull to Hermes, Athene, and Zeus respectively.
On Andromeda's insistence, the wedding took place immediately, even though Cassiopeia insisted that the pledge of her hand had been forced on them by the circumstances, and that Agenor (Phineas), King Belus's twin brother, had already been betrothed to her. The wedding feast was rudely interrupted when Agenor entered at the head of an armed party, claiming Andromeda for himself. "Perseus must die!" Cassiopeia cried fiercely.
In the ensuing fight, Perseus struck down many of his opponents, but, being greatly outnumbered, was forced to snatch the Gorgon's head from the coral and turned two hundred of them to stone.
Poseidon set the images of Cephus and Cassiopeia among the stars. The latter, as a punishment for her treachery, is tied in a market basket which is sometimes turned upside-down. But Athene afterwards honored Andromeda image in a more favorable place because she had insisted on marrying Perseus.
A year later Perseus took Andromeda with him back to Seriphos. She had born Perseus a son, Perses, who was left with Cepheus to be heir to the throne of Joppa. When they arrived, they found that the wife of Dictys was long since dead, and the Dictys himself and his mother Danae had had to flee from Polydectes, who was furious at Danae refusal to marry him. They had taken refuge in the temple. Perseus learned that Polydectes was holding a banquet in the palace with all the men who favored him. Perseus went straight to the hall, with the breastplate of Athena on his chest and the silver pouch at his side. He announced to Polydectes that he had brought the promised love-gift. They poured scorn on his claim to have brought back the head of the Medusa, whereupon Perseus showed it to the king and everyone there and they all turned to stone. This circle of bolders is still shown at Seriphos. He then gave the head to Athene who bore it always upon the aegis, Zeus's shield, which she carried for him. Hermes returned the sandals, pouch, and helmet to the guardianship of the Stygian nymphs.
When the islanders knew they were free from the tyrant, it was easy for him to find Danae and Dictys. He made Dictys king of the island, but he and his mother decided to go back with Andromeda to Argos to try to be reconciled with Acrisius after the many years since he had put him and Danae in the wooden chest. They were accompanied by a party of cyclopses. When Acrisius heard Perseus was coming, he fled to Larissa in Thessaly to avoid the fulfillment of the oracle. When they reached Argos, Perseus found that Acrisius was gone, and where he was no one could say. Perseus had been invited to the althletic funeral games that the King Teutamides of Larissa was holding to honor his dead father. He went to participate, and when he threw the discus, it was carried out of its path by the wind and fell among the spectators. It struck the foot of Acrisius and killed him, fulfilling the prophecy. Greatly grieved, Perseus buried his grandfather in the temple of Athene, and ashamed to reign in Argos, he went to Tiryns where Proteus had been succeeded by Megapenthes and arranged to exchange kingdoms with him.
Perseus fortified Midea, founded Mycenae, so named because when he was thirsty a mushroom (mycos) sprang up, giving him a stream of water. The cyclopses built walls around both cities.
Perseus and Andromeda lived happily ever after. They had five more sons: Alcaeus, Sthenelus, Heleius, Mestor, and Electryon, and a daughter Gorgophone ("slaying of the Gorgon"). Their son Electryon was the grandfather of Hercules.
Note: Graves notes that in the earlies version Proteus is Perseus' father = Osirus. Danae is his sister wife Isis. Perseus is the child Horus, and Acrisius is the jealous Set who killed his twin Osiris and was taken vengeance on by Horus. The ark is the acacia-wood boat in which Isis and Horus searched the Delta for Osiris' body.
He also notes there is a much shorter version without the visit to the three Grays and the nymphs (or any fairy tale stuff). He notes that it is in the story of Hermes that we meet them and he thinks it was just added in when someone confused Hermes with Perseus. The rain of gold is the ritual marriage of the sun and moon for the new year king. He also notes that Libya had a matriarchal system (which might tie in with the Amazons).