Midnight City.

When Serena is told by "Kadinu" the demon that she must murder the hunters, she is scared. The hunters murdered her parents, and that is what gives her the courage to do it.

William loves Tessa. But when she and Jem marry and head off to Ireland, Will is stuck with Charlotte and Henry.
But when The Council finds out about hunters being murdered, they send Will to kill the murderer.
Will goes out in search of a demon, but when he falls in love with Serena, what will happen?
(This is a fanfiction/inspired story based off of Cassandra Clare's series' The Mortal Instruments and The Infernal Devices)