Mary Kathryn Fairchild is Clary Fairchild's twin sister. When their mother starts seeing signs of their shadowhunter world seeping through them. Mary Kathryn for some can't seem to get a block in her mind so she grows up hiding the secret from Clary as long as possible. What happens when Clary is out with Simon and valentines men come for Jocelyn and MK. She makes it out alive but Valentine has their mother and Clary finds out about the new world filled with demons and Angels....that is until Mk meets a blue eyed Shadowhunter.