Karen Daily, recently divorced, lives with her two kids in a quaint suburb of New York City. She's teaching at a nearby elementary school, starting to date again, and for the first time in years has found joy in her life.

Mark Berman, Karen's friend and neighbor, wants out of his unhappy marriage, and so does his wife, Deb, but they have been staying together for their kids. Unbeknownst to Karen, Mark has a rich fantasy life about her, which has grown into a full-blown obsession. As rumors about Karen spread and a bigger secret is uncovered, she becomes a murder suspect and the target of a twisted psychopath.