The movie opens with a nameless, rugged, feral woman (Pollyanna McIntosh) circling what appears as her child. A wolf, apparently tamed by the feral Woman, circles the infant as well but does it no harm. Although it is not fully explained, the Woman is the last remaining member of a human cannibalistic native american tribe that has roamed the north-east coast for decades (as seen in the 2009 film Offspring).
Chris Cleek (Sean Bridgers) is a country lawyer who is shown at a local BBQ with his family. The family enjoys BBQ while the oldest daughter Peggy (Lauren Ashley Carter) sits off to the side clearly detached and upset. Their only son Brian Cleek (Zach Rand) watches as three or four boys violate and push a small girl into a corner. He stands up seemingly to come to her aid, but instead shoots a basketball. As they leave, Chris asks his son how it was to which Brian replies that he shot 9 out of 10 baskets. There is no mention of the girl or anything else.
Later that night while out hunting, Chris happens upon the Woman who is bathing in a nearby stream. He watches her, leaves, and returns later with a net in an effort to capture her. He manages to trap the Woman in the net and knocks her out. Chris returns home with her, restrains her in the storm cellar next to the house, and directs his family to participate in "civilizing" her.
The next day at school with the Woman in the cellar, the kids begin to show their true personalities. Brian is bested by a girl while playing basketball. So later in class, he maliciously puts gum in her brush. She unsuspectingly brushes her hair. He offers aid, but hurts her as he brushes. He appears to enjoy watching her scream in pain.
Peggy is withdrawn at school, detached, and often seen wearing very baggy clothes. Her teacher begins to think she is pregnant and approaches her. Peggy does her best to avoid the topic and returns home.
Chris' first attempt to approach the woman results in her biting off and swallowing the end of his ring finger. She spits his wedding ring out into a pool of blood beneath her feet. Peggy and Chris' long-suffering wife Belle (Angela Bettis) protest and the youngest daughter Darlin' (Shyla Molhusen) attempts to befriend the imprisoned woman. Nonetheless, Chris' will prevails and he orchestrates an increasingly violent series of civilizing measures.
Later that night, Peggy is sitting on her bed, very detached. Her father walks in and sits next her. She is clearly afraid of him. Her mother happens to walk by and quietly watches in the shadows. As Chris begins to talk, he moves closer to Peggy. He tries to reassure her everything will work out because she is very smart and beautiful. Her mother closes in and walks into the room as he kisses Peggy on the forehead. Belle and Chris retire to their room discussing mundane issues. Belle questions Chris' idea of civilizing the Woman considering the two German Shepherds housed in the barn and everything else. He responds by slapping her across the face.
The next day Chris goes to work. He gives the appearance of a sharp, smart, charming man. His innocently flirts with clients and his secretary, but just like his son Brian, Chris is clearly a sadistic sociopath who gets off in emotionally hurting people for his own twisted enjoyment without showing any guilt or remorse. However, in contrast to Brian, Chris hides behind a nice-guy facade that manages to fool everyone whereas the ill-tempered Brian makes little effort to put up his own facade.
At school, Brian continues to maliciously attack his classmates without directly confronting or physically assaulting them. Peggy is seen crying on the soccer field by her teacher. At the end of the day, Chris picks up his kids from school with Peggy being visibly uncomfortable.
At home, Chris baths the Woman with boiling hot water. Belle watches as he caresses the Woman's breast. Belle's mind appears to have snapped as she makes eye contact with the woman. However, she aids Chris in his efforts. Later, Chris decides to bathe the Woman with a high pressure power washer. Belle watches in horror but Peggy, unable to stand it anymore, rushes to the Woman's aid and turns off the power washer. Peggy is forced into the house while Belle and Chris move the woman back into the cellar. There, he dresses her with a gown Belle made for her.
Later that night, Chris sneaks out of bed and rapes the Woman while his son Brian secretly observes. As Chris had entered the cellar, he had turned off the light and lit a candle. This is the same candle seen in his daughter Peggy's room. The implication is that he may have raped his daughter too. The next day, Brian comes home early from school and hurts the woman by stabbing her chest with pliers.
When Peggy catches her brother assaulting the imprisoned woman, she tells her mother who reports the incident to Chris. Chris laughs off the attack as typical of "adolescent urges," upsetting the normally complacent Belle and driving her to announce her intention to leave Chris and take their two daughters, but not their "rapist" son. Chris suddenly reacts violently as he knocks Belle unconscious while Peggy watches with horror, but Brian naturally shows no emotion to his father's abuse towards women. Just then, Peggy's teacher Ms. Raton (Carlee Baker) rings the doorbell. Ms. Raton, suspicious about Peggy's recent depression and baggy clothes, tells Chris that she believes Peggy is pregnant. Chris becomes angry stating that Ms. Raton has accused him of impregnating his daughter and hits her. He and Brian tie her hands and drag her to the barn where he keeps the German Shepherds. Peggy protests, but Chris pushes her away and then subjects her to a vicious verbal assault.
In the barn, Chris and Brian lock Ms. Raton in the dog's cage where the two German Shepherds taunt her. It's soon revealed that the cage also contains an eyeless girl named "Socket" (Alexa Marcigliano) who behaves like the two dogs (Chris references Socket obliquely earlier repeating the word "anophthalmia" several times to Belle). Socket and the dogs kill and eat Ms. Raton as Chris and Brian look on smiling. He later instructs Brian to bring in the wood chipper, rake, and bags because the dogs can never eat it all.
Meanwhile, Peggy releases the imprisoned woman from the cellar. The woman bursts from her dungeon and attacks Belle (who has recently regained consciousness) gnawing off most of her face before tossing her dead body in the air. She then proceeds to the barn where she attacks Brian with a lawnmower blade severing his torso. The Woman then rips Chris's heart out of his chest and eats it. With her psychopath mother, father, and brother dead, a terrified Peggy attempts to escape with her little sister. The formerly imprisoned woman does not attack the girls. Instead, the woman offers her bloody finger to the youngest daughter (who licks it) and then to Peggy (who does not). The feral woman, Socket (acting as the woman's dog), and the young girl walk away from the house apparently forming a new family. Peggy initially just watches them walk away, but then follows them towards the woods.