A man bumps into an old crush and holds her captive underneath the animal shelter where he works.
A psychological thriller about a man who bumps into an old crush and subsequently becomes obsessed with her, leading him to hold her captive underneath the animal shelter where he works. But what will the victim have in store for her captor?
Socially awkward animal shelter employee Seth Donaldson recognizes former Westbrook High classmate Holly Garling riding the same Metro bus. After a brief conversation, Seth goes home and begins researching Holly on social media, specifically by memorizing her likes and dislikes.
With the goal of getting her to go out with him, Seth stages an encounter with Holly at the restaurant where she is a waitress. Holly curtly dismisses Seth after growing uncomfortable with his disclosures regarding what he knows about her.
Seth sends Holly roses, but she confuses them for an olive branch from her ex-boyfriend Eric. Seth follows Holly when she goes to see Eric at the bar where he works. Seth's attempt to talk to Holly turns physical and Eric beats him. Seth recovers Holly's dropped writing journal following the altercation.
Seth builds a cage in the animal shelter's cellar. He then breaks into Holly's apartment and abducts her. By faking a delivery, Seth is able get past the shelter's security guard Nate and he imprisons Holly in the basement.
Holly adjusts to her period of captivity by talking to herself in the form of her imaginary former roommate Claire. Seth eventually confronts Holly about Claire, having read in her journal that she murdered Claire after discovering Claire had an affair with Eric. Seth additionally reveals how he learned from Holly's writing that she became a serial killer after getting her first taste of blood with Claire. Seth tells Holly that his goal is to help her.
Security guard Nate eventually finds Holly. However, Holly willingly distracts Nate so that Seth can stab him. Holly then directs Seth to finish off Nate by caving in his head with a cinder block. She also instructs Seth on how to hide the evidence and dispose of Nate's body.
Seth remains committed to the idea that he and Holly can forge a relationship based on mutual love. Holly continues her ongoing manipulation of Seth's mind. Meanwhile, Detective Meara investigates Nate's disappearance by focusing on Seth as a suspect.
To prove his love for Holly, Seth cuts off his own finger at her insistence. Holly grabs Seth's knife and threatens to kill herself if he doesn't open her cage. Seth frees Holly. Holly tells Seth that she believes he loves her and she loves him back. The two of them kiss before Holly cuts Seth's throat.
Some time later, Holly resumes her romance with Eric and becomes a published author. Holly considers harming Eric after discovering he is cheating on her again. Instead, she goes to a warehouse to see Seth, who is now imprisoned in a cage and mute from his throat injury.
