The Hunters' Night (Her Possession)

"I don't think evil forces exist and even if they do, i could never be haunted by one! That's a flat truth guys!" Finn blurted with a cringe

This is Finn Dexter, is haunted by a young pretty serial killer trapped in an icy coffin in an ancient mansion on the outskirts of the city where he lived. He finds his life in abject terror useless to him. Once he tries to get closer to the truth the more he's compelled to make sacrifices that not even his mother who's a police detective can outrun.
Years ago, long before Finn was born, it is required that a child from each family and generation must carry out the ancient incantations, sacrifices and tasks, Finn finds himself in a situation where he is claimed to be chosen one? Why was he chosen and how does he break the curse?