"The Watcher" follows Julia (Maika Monroe) as she moves to Bucharest after her husband Francis (Karl Gusman) gets a promotion at work. The movie begins with the happy couple arriving in the city and going to see their new apartment. Right in the heart of the city, the apartment is nice, but Julia notices a problem with it right away. An entire wall of windows faces another apartment complex across the street, and before too long a mysterious figure in the other building is watching Julia on a daily basis.
The more that Julia becomes concerned with the man watching her from the other building, the more she starts to feel paranoid everywhere she goes. What makes matters even worse is that Julia's paranoia might actually be based in reality. One day she goes to a nearly empty movie theater, and shortly after the movie begins, a man sits directly behind her. Julia gets up to leave, only to notice the man following her out a few minutes later.
Julia tries to express her anxiety to Francis, but he doesn't take her concerns all that seriously. Eventually, after some intense prodding from Julia, Francis helps her make a complaint about their neighbor Danieto the police. That's when things go from bad to worse. A couple of days later, the police officer shows up at Julia's apartment. Her neighbor, a man named Mr. Weber (Burn Gorman), has come along because he's filing a complaint accusing Julia of following him around.
