Answer:
Perseus cuts off Medusa's head and brings it back to King Polydectes. He turns everyone to stone using Medusa's head and saves his mother.
Perseus cuts of Medusa's head and runs into a trapped princess along the way. He saves her from the Sea Monster coming to eat her by turning it to stone using Medusa's head.
Explanation:
I have heard/read many different versions of this story. I don't know which one you're asking for, so I wrote the two popular ones.
