In the opening scene, a young couple named Michael and Madeline are having sex, attempting to conceive. It is soon apparent that they have succeeded. Michael's parents arrive for dinner: a vegan meal prepared by a now visibly pregnant Madeline. Michael's domineering mother Vivian grimaces at the food and suggests - in a passive aggressive fashion - that a more conventional diet would be healthier for the unborn baby. The conversation turns to the couple's unsuccessful search for a suitable obstetrician. Madeline has rejected Vivian's preferred doctor and friend, Dr. Sohn. Instead she has decided to consult Patricia, her old friend and midwife at an independent clinic. Vivian does not hide her disapproval. Though Michael is also skeptical, the couple visit the clinic for a tour. They meet with Patricia, who describes her natural approach to birthing. Madeline reveals that she and Michael have conceived twice before, but both pregnancies were unsuccessful.One night, Michael rushes Madeline to the hospital because of chest pain. Dr. Sohn arrives at Vivian's request. Just before he administers drugs to induce labor, Patricia arrives. She challenges his diagnosis and determines through blood work (which he has ignored) that inducement is not necessary. Madeline is treated and later released. On the way home from the hospital, a car accident kills both Michael and the unborn baby.Madeline refuses to go to the hospital to have the dead fetus removed. Patricia allows Madeline to carry the dead fetus to term and some weeks later the baby is delivered in Patricia's birthing tub. Madeline is left alone with the stillborn baby and pleads for her to live. Patricia returns to reason with Madeline, to find the baby miraculously alive. Overjoyed, Madeline names the baby Grace.Patricia later visits Madeline at home. She encourages Madeline to take Grace to the hospital for tests to help understand how she revived. Citing her recent experience with Dr. Sohn, Madeline refuses any involvement with conventional medicine. When Patricia reaches out to stroke Madeline's face, Madeline rebuffs her. Patricia leaves, visibly upset.As Madeline cares for the infant Grace, she tries to ignore strange happenings that occur. She resorts to hanging fly paper in the nursery because Grace is attracting them. She is unable to rid the house of a putrid smell and soon realizes that Grace is the source, though her diaper is not soiled. She decides to bathe her, but Grace's skin begins to bleed in the warm bath water. Madeline tries to contact Patricia for help, but can only reach the clinic's answering machine and Patricia's jealous lesbian girlfriend, who does not pass on her messages. After attempts at feeding Grace end with vomiting, Madeline realizes that the baby is unable to digest breast milk.Vivian, who has a pathological relationship with her husband, wants to visit the baby and attempts to call Madeline on the phone, but she will not answer. She visits Dr. Sohn and convinces him to visit Madeline while looking to collect proof that she is an unfit mother. She intends to have Madeline arrested and raise Grace herself.Madeline discovers that Grace's nursing is painful to the point of causing her breast to bleed. She soon realizes that the undead child is actually feeding on her blood. She buys raw beef, drains the blood, and is able to get Grace to drink it from a bottle. While disposing of the leftover meat outside, she almost catches Patricia spying on her from her car. She returns indoors to find Grace vomiting up the cow's blood, leaving Madeline no choice but to continue to feed Grace from her own bleeding breast. Each feeding becomes more gruesome and Madeline begins to become dangerously weak.Madeline becomes so sick and distraught that she allows Dr. Sohn into her home when he calls on her. He examines her, explains that she is anemic, and instructs her to refrain from nursing for a few days. After hearing Grace cry weakly, he starts upstairs, while dialing Vivian's number on his cell phone. Fearing that he will take Grace away from her, Madeline beats Dr. Sohn unconscious, but not before his call connects.Vivian arrives just as Madeline finishes draining blood from Dr. Sohn's arm into a baby bottle. Vivian notices the unkempt state of the house and suspiciously remarks at Madeline's sick appearance. She agrees to leave, but instead sneaks upstairs. She finds Grace in her crib, and the bottle of Dr. Sohn's blood broken on the floor. Madeline hears her and climbs the stairs, but Vivian is able to grab Grace and sneak into the bathroom. While seeking a place to hide, she discovers Dr. Sohn's body. She arms herself with a hammer she brought along and sneaks down the stairs with Grace. Madeline confronts her, and the two fight. Vivian beats Madeline unconscious with the hammer, but not before Madeline rips out part of her throat with her teeth. They are discovered by Patricia, who realized her girlfriend was withholding Madeline's messages and decided to investigate.Some time later, Patricia is driving a motor home through the desert. She pulls over and goes to the back to check on a very-much alive Madeline and Grace. Both women have changed their hair or donned wigs. Patricia asserts that medical tests have confirmed Grace is as healthy as she looks. As long as Madeline keeps eating the proper diet, they can continue feeding and raising Grace. Madeline is concerned about something else, however: the natural-born zombie Grace has begun teething. She pulls up her shirt to reveal that a large chunk of her breast has been chewed away....