Hamilton draws the story of Perseus from the later writers Ovid and Apollodorus, though it was also widely popular among the Greeks. One day, the Oracle at Delphi tells King Acrisius of Argos that the future son of his daughter, Danaë, will kill him. Though Acrisius imprisons Danaë to prevent her from ever getting pregnant, Zeus magically enters the prison. Danaë gives birth to a son, Perseus. Acrisius locks Danaë and Perseus in a chest and casts it to sea.
Danaë and her son eventually wash up at the home of Dictys, a kind fisherman whose brother, Polydectes, is the cruel ruler of the area. Polydectes soon wants to get rid of Perseus and marry Danaë, so he comes up with a plan to kill the young man: he convinces Perseus to go kill Medusa, the horrible Gorgon—an impossible feat for a mortal. The gods favor Perseus, however: he receives a mirrored shield from Athena, a magic sword from Hermes, and information on the location of the nymphs of the North—the only ones who know how to kill the Gorgon—from the Graiae, three supernatural gray sisters with only one eye among them. Perseus craftily steals the eye the Graiae share and refuses to return it until they help him. He eventually reaches the mystical land of the Hyperborean nymphs, who give him winged sandals that allow him to fly, a wallet that expands to hold anything, and a cap that makes its wearer invisible. With these, Hermes’ sword, and Athena’s mirrored shield—which enables him to avoid looking directly at the Gorgons, which would turns him to stone—he creeps into the Gorgons’ cave while they are sleeping. The two gods point out Medusa, the only mortal one. While looking at her in the mirror, Perseus chops off her head and puts it in the magic wallet, then begins to fly home.
Along the way, he comes upon Andromeda, a princess who has been chained to a rock because her mother, Cassiopeia, has offended the gods. A sea serpent is about to eat Andromeda, but Perseus cuts off its head and takes Andromeda as his wife. He returns home to find that Polydectes has driven his mother and Dictys into hiding. Perseus goes to Polydectes’ palace where all the evil men of the kingdom are gathered. He marches into the meeting and reveals Medusa’s head, turning all the men to stone. He lives happily ever after but only after unwittingly fulfilling the prophecy of the Oracle: while participating in a discus-throwing contest, Perseus accidentally hits and kills a spectator, who is, unbeknownst to him, his grandfather Acrisius.
Hamilton’s account of Theseus, the greatest hero of Athens, again draws upon Apollodorus, but it also stitches together details from other writers, some as early as Sophocles. Theseus is the son of the Athenian king, Aegeus, but he grows up with his mother in the south. Aegeus has left a sword and pair of shoes under a giant rock and says that when Theseus gets strong enough to move the rock, he is to be sent to Athens. Theseus reaches maturity, rolls the rock aside, takes the sword and shoes, and sets out on the journey. The dangerous road to Athens is full of bandits, notably Sciron, Sinis, and Procrustes, who delight in torturing passersby. Theseus kills the bandits in the same methods they have used to kill their own victims.
When Theseus arrives in Athens, the evil Medea senselessly convinces Aegeus, who does not realize the stranger is his son, to kill him. At the last minute, Aegeus sees the sword and recognizes the boy. Medea escapes to Asia. Theseus then saves Athens from its obligation to King Minos of Crete. After a son of Minos was killed while a guest in Aegeus’s household, Minos beat the Athenians in a war, and now, as punishment, every nine years the Athenians had to send seven girls and seven boys to meet their doom in the Labyrinth of the Minotaur. Theseus offers himself as a victim, promising his father that if he survives, he will replace his ship’s black sail with a white one for the return journey so that Aegeus will be able to tell whether his son is alive.
Like Jason, Theseus wins the heart of the enemy king’s daughter, Ariadne, who defies Minos and helps Theseus escape the Labyrinth with a ball of golden thread that he unwinds as he walks so that he can find his way back. Theseus finds the Minotaur asleep, beats it to death, and flees to the ship to sail home. Ariadne flees with him, and on the way home, he abandons her when she goes ashore and a fierce wind blows him out to sea. Ariadne dies, which is perhaps what makes Theseus forget to lower the black sail and raise the white one. When Aegeus sees the black sail approaching, he commits suicide by jumping into the sea then named after him—the Aegean.