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. Sofi explains that she had a twin brother who was killed in Nazi experiments in Auschwitz when they were both just children. The boy was brought back to life by a dybbuk who intended to use his body as a portal into the world of the living. Sofi killed her twin to stop the dybbuk, and now it haunts her family for revenge. Sofi refers Casey to Rabbi Sendak (Gary Oldman), who can perform a Jewish exorcism to remove the dybbuk. The exorcism is performed, but things go awry as the dybbuk tries to stop Rabbi Sendak from completing the ritual. The dybbuk disappears after the exorcism and the death of Casey's boyfriend. Soon afterward, Casey learns she is pregnant with twins.