Perseus's mother Danae is imprisoned in a tower by her own father after a prophecy warns that her son will kill him, but Zeus visits her as a shower of gold and Perseus is born regardless; both mother and child are later set adrift at sea in a chest and wash up safely on another island. Grown to manhood, Perseus is sent by a king who wants Danae for himself on what is meant to be a fatal errand: bring back the head of Medusa, one of three monstrous Gorgon sisters whose gaze turns any living thing that meets it instantly to stone, and the only one of the three who is mortal.
The gods equip Perseus for the impossible task: Athena gives him a polished bronze shield to use as a mirror so he need never look at Medusa directly, Hermes gives him winged sandals for flight, Hades lends a cap of invisibility, and he obtains a curved sickle-sword and a pouch to safely carry the severed head. Guided to the Gorgons' lair, Perseus watches Medusa's reflection in his shield, approaches her while she sleeps, and beheads her with a single stroke; from her blood spring the winged horse Pegasus and the warrior Chrysaor, both conceived earlier with Poseidon.
Before reaching the Gorgons at all, Perseus first had to locate them, information held only by the Graeae, three ancient sisters who shared a single eye and a single tooth between them, passing each back and forth. Perseus intercepted the eye as it changed hands and refused to return it until the sisters told him where to find both the Gorgons and the nymphs who could equip him with the tools he still needed.