Who would the antagonist be in the book This Lullaby by Sarah Dessen?

I have a en English project where I have to make a CD (not an actually CD just listing song titles). One song about the setting, 3 songs about characters (the protagonist, antagonist, and supporting character) 1 song about the conflict, and one about the resolution. Its an independent reading choice book and I picked This Lullaby I know Remy is the protagonist and I ume Dexter is the supporting character but who would be the antagonist?