The terrified king consulted the oracle of Jupiter. They said that Neptune could only be satisfied by sacrificing Cassiopeia's only virgin daughter to the monster. Andromeda was chained to a rock on the coast, fully exposed to the monster. Fortunately for her, Perseus, her hero, was flying by on his way from killing the Gorgon Medusa:
When he saw her she would've been mistaken for a marble statue. He fell in love immediately. Amazed at the sight of beauty, he almost forgot to keep his wings moving. As he stopped, he called out, "You shouldn't be wearing those chains- the right bonds for you are the ones in which bind the hearts of fond lovers! Tell me your name and the name of your country, and tell me why you are in those chains."
She didn't speak to him because she is a girl and she wasn't supposed to talk to a man. She would've hid her face with her hands, but they were tied up. She started crying instead. When Perseus kept on questioning her she finally gave in. She told hime the name of her country, her own name, and how her mother had been too confident in her beauty.
But before she finished, the waters started to get higher and higher until the menacing sea monster came. The girl screamed and her sorrowing mom and dad was close at hand. They were both upset though the mom had more cause to be so.
Perseus says that he'll kill the monster if her parents agree to let him marry her. They let him do that, so and he kills the monster. (His method is variable in different versions of the myth. Ovid has him stab the monster to death after a bloody battle, while others say that Perseus holds up the head of Medusa, turning the monster to stone.) Andromeda is let go, and the two get married.
Andromeda is seen in the sky as a woman with her arms outstretched and chained up at the wrists.