Well it is in the title... Jace cheats on Clary she Leaves heart broken then moves on and has to return years later for demon related reasons!!!

Don’t miss this imaginative new short story set in the magical world of Watersong—a realm of enchanting beauty…and terrifying secrets. Aggie is a mythological creature on a secret mission. Lydia is a young woman from a magical family with no real powers of her own. And Daniel is a high school boy who’s made it his duty to protect his deeply troubled older brother. Then one fateful night, their lives collide in a terrifying accident that changes them all forever. And beneath the surface, the ripple effects of the accident will have more impact than anyone could ever guess...changing not only their future, but the fate of an entire town.

Can you still love the one that hurt you most? TMI fanfic 1st) Gone 2nd) Stay 3rd) Together Forever