Actually had a idea for something like this, but the protagonist was the 6 year old, and was freed after 10 years. Then she was recruited by a agency to find the people that murdered her parents and framed her.
Everyone is born with blond hair. Their hair turns brown when they lose their innocence. I was born with black hair. I will lead the revolution. (Not really anything to do with the story but I just thought it was good.)