When Perseus arrives to the place where the Gorgons lived, with Athena's help he was able to find who was Medusa, and decapitate Medusa with his unbreakable sword while she and the other two were sleeping, Perseus placed the hissing snakes and Medusa's head in the magical wallet.
The Road Back
But before Perseus could escape, the two other immortal Gorgon sisters had awoken, furious at the sight of Medusa's body with no head. Ready to annihilate the one who had killed her, the two sisters did't know Perseus had escaped with the invisible cap.
With Perseus's hand was his reward of Medusa's head, he was able to free his mother from the Polydectes, and now Perseus was a hero, being known as the one who slayed Medusa. His name would be remembered as the stalwart hero, Perseus had proven his worthy and how brave he was.
Return with the Elixir
On Perseus' way back with the winged sandals, he finds the beautiful princess Andromeda getting attacked by a vicious sea monster. Perseus again showed his bravery by fighting and slaying the sea monster, in return with great gratitude, Andromeda goes home with Perseus in plans to be his consort.
With Perseus' return to his home, Polydectes refuses to accept the fact that Perseus had slew Medusa. Only then did Perseus realize Polydectes only sent him inorder to get rid of him, Perseus reveals the head of Medusa only for Polydectes to be turned into stone. The perilous times with the cruel king was over.
Perseus and his great journey as a hero over, he returned home to the land Dictys' ruled, his mother free from the evil Polydectes and his beautiful wife Andromeda. With the prophecy fulfilled, Perseus killed his grandfather and lived his days known as a hero who slayed Medusa.