The following is a summary of Edith Hamilton's take on Jason and the Golden Fleece by Apollonius of Rhodes (SparkNotes).
Hamilton’s account of the Golden Fleece comes from Apollonius of Rhodes, a Greek poet from about 300 b.c. Athamas, a king, gets tired of his first wife, Nephele, and marries a second, Ino. Ino wants Nephele’s son, Phrixus, out of the way so her own son can inherit the throne. Hermes sends a flying golden ram to rescue Phrixus and his sister, Helle, who falls off the ram and dies. Phrixus safely reaches the land of Colchis, where he sacrifices the ram to Zeus and gives its skin—the Golden Fleece—to Colchis’s king, Aetes.
Meanwhile, a man named Pelias has usurped the throne of Phrixus’s uncle, a Greek king. Jason, the deposed king’s son, grows up and returns to reclaim the throne. En route to Pelias’s kingdom, Jason loses a sandal. Pelias is afraid when he sees Jason approach, as an oracle has told him that he will be overthrown by a stranger wearing only one sandal. The wicked Pelias pretends to acquiesce but says that the gods have told him that the Golden Fleece must be retrieved for the kingdom first. This is a lie—Pelias assumes that anyone sent on that dangerous journey will never come back. Jason, intrigued by the challenge, assembles a remarkable group of heroes to help him, including Hercules, Theseus, Peleus, and Orpheus. Their ship is named the Argo, so the group is called the Argonauts.
The Argonauts face many challenges on the way to Colchis. They first meet the fierce women of Lemnos, who have killed their men, but find them atypically kind. Hercules leaves the crew, and the Argonauts meet an oracle, Phineus. The sons of Boreas, the North Wind, help Phineus by driving off some terrible Harpies who foul his food whenever he tries to eat. Phineus gives the Argonauts information that helps them pass safely through their next challenge—the Symplegades, gigantic rocks that smash together when a ship sail through them. After narrowly avoiding conflict with the Amazons, bloody women warriors, and passing by the chained Prometheus, the Argonauts finally arrive at Colchis.
Though more trials await here, Hera and Aphrodite help Jason. Like Pelias, Aetes pretends to want to give Jason the Fleece but first demands that he complete two tasks that are designed to kill him. Aphrodite sends Cupid to make Aetes’s daughter, a witch named Medea, fall in love with Jason and help him through the tasks. The first challenge is to yoke two fierce magical bulls with hooves of bronze and breath of fire, and Medea gives Jason an ointment that makes him invincible. The second task is to use the bulls to plow a field and sow it with dragon’s teeth, which causes armed men to spring up from the earth and attack Jason. Medea tells him that if he throws a rock in the middle of the armed men, they will attack each other, not him. After Jason’s success, Aetes plots to kill the Argonauts at night, but Medea again intercedes, warning Jason and enabling him to steal the Fleece by putting its guardian serpent to sleep. Medea joins the Argonauts and flees back to Greece. On the way home, she commits the ultimate act of love for Jason: to help evade the ship’s pursuers, she kills her own brother, Apsyrtus.
On the way home, the Argonauts pass more challenges, including safely navigating Scylla, the dreaded rock; Charybdis, the whirlpool; and Talus, the giant bronze man. Upon returning, Jason finds that Pelias has killed his father and that his mother has died of sadness. Jason and Medea plot revenge—Medea convinces Pelias’s daughters that they will restore Pelias to youth if they kill him, chop him up, and put the pieces into her magic pot. Out of love for their father, they slice him to bits, but Medea leaves the city, taking her magic pot with her after first restoring Jason’s father to life.
Medea and Jason have two children, but Jason leaves out of personal ambition to marry the daughter of the king of Corinth, who banishes Medea and her children. Infuriated by the unsympathetic Jason, Medea enacts a terrible revenge, sending her two sons with a beautiful magic robe as a gift for Jason’s new bride. When the girl dons the robe, it bursts into flame, consuming her and the king as he rushes to her. Medea then kills the two sons she had with Jason and flies away on a magic chariot. This tragic final chapter in the story of Jason and Medea is the subject of Euripides’ play, Medea.