Plot
In Onatah County, Anna spends her childhood confined to the basement by her father, who warns her of a child-eating monster called "The Wildling" roaming the forest. When Anna reaches puberty, "Daddy" gives Anna daily injections of leuprorelin, explaining that he is treating her "illness." The injections, which prevents her body from maturing, causes painful side effects from the injections. When Anna asks Daddy to kill her, Daddy cannot bring himself to shoot her and instead shoots himself.
Anna awakens in hospital where she was treated for the overdose. Sheriff Ellen Cooper tells her that Daddy has survived, but is in critical condition. Anna temporarily stays at Ellen's home until her relatives can be identified and located. She befriends Ellen's younger brother Ray and attends high school with him. When Anna finally enters puberty, she develops superhuman hearing and feels drawn to the forest and the Northern Lights. A DNA test reveals that Daddy is not Anna's biological father.
Ray takes Anna to a party. They share a brief kiss before Ray notices that Anna's mouth is bleeding. After rushing to the bathroom, Anna loses several teeth and flees out the window. Local bully Lawrence finds her in the woods. He strips off her dress and tries to rape her, but she rips out his throat with her teeth. Confused and frightened, Anna realizes that sharper teeth are pushing out her human teeth, and her fingernails are slowly becoming claw-like.
Stumbling around half-naked, she comes across the house of "Daddy" where she showers the blood off and puts on some clean clothes. The next day, she walks back into town and is picked up by Ellen. Later in the forest, Anna encounters a one-eyed outdoorsman. He tells her that he has not seen one of her kind since the townspeople conducted "the purge" sixteen years ago. He also explains that she will find her mother in a nearby cave. There, Anna discovers a fanged skull with a bullet hole in the forehead. She suddenly remembers "Daddy" shooting her mother during the purge. "Daddy" could not bring himself to kill baby Anna and instead raised her as his daughter and kept her hidden from the outside world.
Anna returns to Ellen's home where Ellen handcuffs her and takes her to jail. Ellen explains that the police have discovered Lawrence's body next to Anna's dress. Later that night, "Daddy" visits Anna and tells her that sparing her life was his greatest mistake, as he broke his oath "to kill all the Wildlings." He hands Anna a syringe with a lethal dose of leuprorelin and urges her to take it, but she refuses.
The next morning, Ellen checks on Anna, who manages to lock Ellen in the jail cell and escape. Anna convinces Ray to drive north towards the forest. Abandoning the car, they go into the forest where they have sex as Ray feels hair growing on Anna's lower back. The next morning, Anna discovers claws have grown on her feet. "Daddy" and a group of hunters ambush them, shooting Ray in the arm as they escape. Anna splits off from Ray and leads the hunting party away.
Three months later, Anna has almost fully transformed into a Wildling sporting darker skin, hair on parts of her body, and a near-deformed face. Ellen follows the hunters on one of their expeditions. Anna kills several hunters, but Ellen allows her to escape after seeing that she is pregnant. The hunters set the forest on fire, forcing Anna to dig underground, undergoing further transformations in the process with big hands and stretched out feet as she rips off her clothes. "Daddy" ambushes Anna and tranquilizes her, intending to perform a Caesarean section to take out the unborn child. Anna fights off the drugs, unhinges her jaws, and rips his throat out before collapsing. Anna awakens to find the outdoorsman stitching her wounds.
The next morning, Ellen and Ray see Anna from afar as she runs back towards the mountains in a northern direction. Sometime later in the far north, a fully transformed Anna cradles her newborn child under the Northern Lights, she hears the call of another Wildling.
