Cooper Daniels lives next door to a psychopath . He just can't prove it ... yet . When the most popular girl in high school is murdered at a Halloween party , Cooper's suspicions become a reality . He knows exactly who did it . But how is he supposed to prove his charming neighbor is a killer ? Meanwhile , Calla Parker is waking up with blood under her nails , and she has no idea why . Unable to remember the night before , Calla begins to suspect herself of murder . She's relieved to find out the police have zero evidence to go on . Yet she can't help but shake the feeling she's being watched - very closely . And she knows why . Cooper Daniels knows her secret.