It doesn't take much to push you over the edge...

When Sydney Horner sends her abusive boyfriend to jail, she thinks her days of torture are over. After she takes the detective's advice to try out therapy, little things begin to happen. The television remote moved. Her car in a different spot. Her clothes missing. Footsteps when she's in the shower.

At first, everyone thinks Sydney is paranoid—suffering from PTSD from her boyfriend and childhood trauma she hasn't told anyone about, her twin sister's death after she tried to kill Sydney. But Sydney knows better, that someone's trying to torment her. And if she doesn't find them soon and figure out why they're doing this, those little things won't stop there...