McPhee, a former American Idol contestant, will play an assistant to Bentley's writer who begins to investigate whether her boss's muse and narrator for his stories is just a figment of his imagination. Anita Briem will star as the muse.
Robert Angelo Masciantonio will direct the film.
McPhee recently completed work on Anna Faris comedy The House Bunny. Bentley's credits include American Beauty, The Four Feathers and Ghost Rider.