After Cadmus and Harmonia become serpents, India and Greece join Bacchus’s cult. However, Bacchus is forbidden to enter Argos by its ruler Acrisius, who denies that Bacchus is Jupiter’s son. Acrisius also denies that his grandson Perseus is Jupiter’s son. Perseus flies around in exile, carrying the head of Medusa—a maiden with snakes for hair—as a trophy. Where drops of blood from the head fall, hordes of serpents appear. As it grows dark, Perseus lands in the kingdom of Atlas, hoping to rest for the night. Atlas is a mighty and famous ruler, and his vast kingdom is surrounded by golden apple trees.
One of the main arguments for not worshipping certain gods is that there is no proof that these new gods—Bacchus and Perseus—are the sons of real gods like Jupiter. Since the gods rarely appear to people in their divine form—not even to the human women they have children with—it is impossible for anyone to have proof of a person’s divine lineage unless they have faith in it. As it did in the story of Phaëthon, doubt about one’s descent can cause unrest in the human world.
Perseus tells Atlas that he is the son of Jupiter. Atlas, remembering a prophecy he once heard that said the son of Jupiter would steal his golden apple trees, tells Perseus to leave. Perseus holds his ground and pulls out the head of Medusa. Instantly, Atlas turns into a huge mountain jutting up into the clouds.
Perseus turns Atlas to stone with the Medusa head, proving that he has a god’s power and punishing Atlas for his lack of respect. The gods do not want to prove their power to humans but expect humans to blindly embrace and worship their power.
Perseus spends the night in a cave. In the morning, he puts on his winged sandals and takes flight. After a while, he comes across a girl tied to a cliff over the ocean. This girl—Andromeda—is being unjustly punished for her mother’s arrogance. Perseus is captivated by Andromeda and lands beside her. He flirts with her, and she blushes shyly and tells him her story. Suddenly, a monster appears from the waves. Andromeda’s parents run to their daughter, regretting their cruelty. Perseus promises to rescue Andromeda if they will let him marry her. They agree and promise him their kingdom as a dowry.
Although Perseus is part god, he lives in the human world and gets wrapped up in its affairs. He negotiates with the people in Andromeda’s kingdom, wanting to obtain Andromeda as a wife and her kingdom as his to rule. In saving Andromeda, who is being unjustly punished, Perseus brings justice, but also secures a place for himself in the world and people whom he can persuade to worship him.
Perseus flies on his winged sandals to meet the monster. They fight until Perseus, bracing himself against a rock, spears the monster in its vital organs. The kingdom rejoices, and Andromeda’s parents give Perseus their daughter. Perseus puts the Medusa head on a bed of seaweed. The seaweed hardens into a new plant which populates the sea today as coral.
Although Perseus is a god and has powers at his disposal—such as Medusa’s head—he fights the monster as if he were a mortal. This suggests that Perseus wants to gain honor in the eyes of Andromeda’s people by winning a fight with only human skills.
In his new kingdom, Perseus builds sacrificial altars to Mercury, Minerva, and Jupiter. He and Andromeda have a regal wedding. Perseus tells how he obtained Medusa’s head: he stole a seeing eye from two sisters in Atlas, then went to the land where Medusa glared at men and animals until they turned to stone. While Medusa slept, Perseus cut off her head. Perseus explains that Medusa was once a beautiful woman with many suitors. Then one day, Neptune raped her. Minerva saw the rape and punished it by transforming Medusa’s tempting hair into menacing snakes.
Medusa is originally given a head of snakes and the power to turn people and animals into stone as a kind of retribution for having been raped. Following her rape, anyone who tried to approach her would be turned to stone. Perseus cuts off Medusa’s head and uses it as his own weapon, an action which does not endow him with nobility. Rather, it seems that Perseus’s power comes only from the stolen weapons of other gods.