Camille nicknames her newborn daughter Sweetheart and posts a carefully edited photo that obscures both of their concerning physical features online. It earns her 60,000 likes and a follow from her influencer idol, Mara. Camille lies to Graham about the birth, and he remains oblivious to the strange circumstances surrounding Camille’s labor and Sweetheart’s abnormalities. Instead of normal postpartum bleeding, Camille discharges wet soil.

Sweetheart has not eaten since birth; she refuses formula, and Camille has no breast milk. One day, Sweetheart suddenly bites off two of Camille’s toes. After eating them, she drinks the blood from the wound, which then heals into a scar. Camille discovers Sweetheart has a full set of sharp, fang-like teeth. When Sweetheart later rejects raw hamburger meat, Camille cuts a piece of flesh from her own stomach to feed her. Sweetheart eagerly consumes it and drinks from the new wound, which also heals over. Accepting this as a necessary maternal sacrifice, Camille posts another curated photo of her sleeping daughter.

Renee visits unannounced to see Sweetheart, who is asleep. Renee offers to babysit and warns Camille about the nearby forest once again, mentioning local legends about missing animals and hunters. 

Later, Camille hosts a live video to introduce Sweetheart to her social media followers. During the stream, viewers question her authenticity as a “tradwife” and bring up her past as a scientist. Camille is forced to end the video abruptly when Sweetheart begins to wake up, fearing that her viewers may see her daughter’s inhuman eyes.

Camille notes that Sweetheart’s bodily waste is also unusual, consisting of white urine and soil-like feces. She feeds Sweetheart by cutting off more of her own flesh. Afterward, she sees a shadow at the back door and discovers that the creature has left a dead hare on her patio.

Graham comes home for a “date night.” Before dinner, Camille moves the dead hare, hiding it by the side of the house while fighting a powerful urge to eat it. 

During a tense dinner, Camille feels increasingly disconnected from her husband. Later, when Graham initiates sex, she refuses him for the first time in their relationship, claiming she needs more time to recover from childbirth. Graham is visibly shocked and resentful.

After Graham falls asleep, Camille slips outside and devours the raw hare. The fresh meat is intensely satisfying and tastes far better than the store-bought raw meat she has been consuming. She throws the bones into the adjacent wheat field, sensing that the creature is watching her from the darkness.

A month after Sweetheart’s birth, Camille feels overwhelmed by her new life, which involves constant chores, managing her social media, and secretly consuming the dead animals the creature provides. Graham has become more distant since Camille rejected him sexually. He notices Sweetheart’s rapid growth and strange skin tone but accepts Camille’s dismissive explanations for them. She successfully convinces him to postpone Sweetheart’s baptism until the spring, buying more time to conceal her daughter’s nature.

After reading a post online, curiosity leads Camille to ask Graham about fallen angels. Graham explains that they are angels who were cast out of Heaven for sins, including mating with human women to create giant offspring called Nephilim. Camille realizes the creature who fathered her child is a fallen angel. She accepts this truth and resolves to protect Sweetheart at any cost.

During a nighttime feeding, Sweetheart’s hunger has clearly grown. She latches onto Camille’s thigh with new aggression, refusing to stop feeding and beginning to chew the flesh. Camille is forced to pry her daughter off, tearing her own leg and leaving a much larger wound than usual. The incident solidifies her understanding that Sweetheart is not human and that she must be more cautious.

Later, Camille goes into the wheat field to eat a dead sheep left by the creature. She discovers the creature has thoughtfully woven a mat of wheat for her to kneel on. As she eats, she notes that even this fresh animal meat is becoming less satisfying. Sensing the creature watching, she raises a hand in acknowledgment before returning to the house, wondering how much longer she can maintain her secret life.

Camille attempts to feed Sweetheart by draining her own blood into a baby bottle, but the amount is insufficient, and the baby cries inconsolably from hunger. 

After seeing cruel online comments about her daughter’s appearance, Camille decides to stop posting photos of Sweetheart to protect her. Her neighbor, Renee, arrives unannounced and makes similarly critical remarks about the baby’s size and skin tone. Ignoring Camille’s wishes, Renee picks up the sleeping Sweetheart. The baby awakens, revealing her solid white eyes to Renee for the first time. Sweetheart then bites Renee’s forearm, latching on and drawing blood. As Renee thrashes about, endangering the baby still attached to her arm, Camille grabs a marble rolling pin and strikes Renee over the head.

Camille delivers a final, fatal blow to Renee with a rolling pin. She is shocked to see Sweetheart crawl with surprising speed toward the body. Needing to hide the evidence before her husband Graham returns, Camille drags Renee’s corpse into the wheat field behind their house. Sweetheart follows and begins to eat the body. Camille assists by removing Renee’s clothing, rationalizing that the murder now serves the purpose of feeding her hungry child. 

While watching Sweetheart feed, Camille is briefly tempted to eat the human flesh herself but is ultimately repulsed by the thought. As it starts to rain, she carries her sleeping, blood-covered daughter back inside, leaving Renee’s partially eaten body in the field.