The Unborn is a supernatural thriller that draws upon the legend of a dybbuk, a malevolent spirit that refuses to leave the human world and inhabits the body of a person. Protagonist Casey Beldon (Odette Yustman) is plagued by merciless dreams, visions of strange looking dogs, and an evil child with bright blue eyes. After being hit with a mirror by her neighbor's son, Casey's eyes begin to change color and she learns she had a twin brother who died in the womb. Casey begins to suspect that the spirit haunting her is the soul of her dead twin, being possessed by a dybbuk, wanting to be born so it can transfer to the world of the living. Casey meets a woman named Sofi, who is revealed to be her grandmother.