Kit (Brie Larson), a failed artist, moves back in with her parents (Joan Cusack, Bradley Whitford). Realizing she must conform to adulthood like her parents always wanted, takes up an office job at a temp agency. However, once she receives a mysterious letter from "The Salesman" (Samuel L. Jackson) who invites her to "The Store", the place that sells "what you need", her entire outlook changes. The Salesman offers her the chance to have it all by fulfilling her childhood fantasy: owning a unicorn. The film deals with the all too familiar crisis of choosing whether to pursue a more traditional "adult" life path or truly go after your dreams.