When old-fashioned David and Harriet meet at their office Christmas party, they fall in love and decide to marry. The look for a house outside of London where they can settle down and begin pursuing what they’re surprised to discover is a mutual goal: a large family with as many as ten children. The house they find is enormous and perfectly in line with their dreams, but it’s expensive. They’ll have to wait a couple years to begin having children, ensuring their double income until David moves up the payscale enough in his architecture firm to pay their mortgage alone. Almost immediately, though, Harriet becomes pregnant, giving birth to Luke in 1966. They ask David’s wealthy father, James, for financial help and Harriet’s mother, Dorothy, for help caring for the new baby.
Right away, the house becomes a hub of family life, drawing visitors including David’s father, David’s mother and her husband (Molly and Frederick), and Harriet’s sisters Angela and Sarah and their families. Harriet finds herself pregnant again the same year and the whole family celebrates Christmas at their house. The second child, Helen, is born soon after, and the extended family continues to pay vists. Harriet’s sister, Sarah, quarrels with her husband, William, but a divorce is not possible because they’re expecting their fourth child, Amy, who is later born with Down Syndrome.
The family celebrations continue like this, and meanwhile Harriet and David’s third and fourth children, Jane and Paul, are born. At Easter, William speaks up, saying what the rest of the family is thinking: that Harriet and David should stop having children. Harriet says they plan to wait three years to continue growing the family. Harriet’s sister Sarah, frustrated at the amount of assistance Harriet receives, asks Dorothy to come help her instead and Dorothy complies. Harriet tries three different girls as nannies, but none of them is a fit.
Harriet finds out she is pregnant with a fifth child, and she is finding this pregnancy particularly uncomfortable. When Harriet and David tell Dorothy about the pregnancy, she reprimands them for their lack of responsibility, complaining that they think of her as a servant, but agrees to return to help out with the assistance of one of Frederick’s cousins, Alice. Just a few months in, the fifth child is already moving around quite violently in Harriet’s womb, trying “to tear its way out of her stomach.” Harriet, concerned, visits Dr. Brett, but the doctor insists there is nothing out of the ordinary, prescribing her a sedative for her nerves. Harriet also begs her friends for additional tranquilizers, hiding this dependency from David. Harriet says they can’t host Easter in her current state, but the rest of the family insists—the atmosphere has become hostile with the stress of the imminent pregnancy.
At eight months, the labor pains begin, and Harriet gives birth to an eleven-pound boy, caveman-like in appearance and surprisingly strong. They name him Ben. The child is violent in all his actions, including breastfeeding, and he doesn’t show any signs of recognizing his family. Harriet also doesn’t feel the same affection for this child that she did for her older children. Almost immediately they wonder: “What is he?” Attempts at answering this question, whispered through the family, include: goblin, dwarf, troll, changeling, gnome. Harriet and David stop having sex, worried they’ll inadvertently create another child like Ben.
Harriet shuts Ben in his room alone because of the threat he poses to others, but Ben sprains Paul’s arm by pulling it through the bars on his crib, and then a dog and cat turn up dead, seemingly victims of Ben’s violence. Fewer guests visit the house, since they’re frightened of the strange child. When Ben is 18-months-old, Dorothy offers to watch him alone for a week so the rest of the family can get away. They take a vacation to France and feel immediate relief. When they return, Dorothy delivers a difficult suggestion: “Ben has got to go into an institution.” They refuse this idea and Harriet begins devoting her attention to Ben alone.
Ben begins to talk in short sentences, mimicking the speech and action of his siblings, but unable to replicate these gestures on his own. The Christmas after Ben turns three, the extended family sees Ben stalking the large dog that is Amy’s companion and protection, prompting Frederick also to recommend they put Ben in an institution. David asks how they’ll pay for such a thing without any sort of diagnosis, and both sets of his parents agree to contribute. Unhappy with their insistence, but awakened to its necessity, David takes over the process of transitioning Ben out of the home. Harriet, knowing that Ben won’t be expected to live long in such an institution, protests, and David claims that Ben is not his son. Once Ben is placed in a van to the institution where he’ll stay, the relief in the family is palpable. However, Harriet can’t stop herself from thinking about what’s become of Ben, and she insists on visiting him.
At the institution, Harriet races past dozens of drugged and disfigured children to find Ben clothed in a straightjacket and nothing else, lying unconscious on a urine-soaked cot. Seeing this, she knows she must bring him home. The orderlies, concerned at how she’ll manage him, send her off with sedatives for the ride home.
At home, the family is horrified to find Ben in Harriet’s arms. She realizes that her only way of controlling him is to threaten to take him back to the institution, which proves effective in mitigating his destructive behavior. David remains detached from Ben. A young man named John does yard work for the family and Ben takes a liking to him. Harriet proposes that John serve as Ben’s nanny, allowing Ben to tag along wherever John and his friends go. John agrees.
Harriet and David go on a weekend trip alone to reconnect. Harriet suggests having more children and David absolutely refuses the possibility. Family arrives for the summer holiday, but not Molly and Frederick who cannot forgive Harriet for bringing Ben back from the institution.
Harriet and David can no longer lock Ben in his room at night and so the other children lock themselves into their rooms, barring Harriet from tucking them in or checking on them. When Ben is five, Luke and Helen request to be sent to boarding school, their grandparents having already agreed to foot the bill because none of them like Ben. It also becomes apparent that Paul is emotionally disturbed because of the neglect he’s suffered. Ben is finally of age to go to school, and Harriet anticipates horrible news from his teachers, but they insist that, despite his not picking up on the lessons, he tries very hard. At the end of the second term, though, Ben acts out, knocking down a little girl, biting her, and breaking her arm. Harriet threatens to return him to the institution and John also talks to Ben, explaining why he can’t hurt others.
Harriet also asks Dr. Brett to arrange an appointment with a specialist. She worries that he’ll forewarn the doctor that the issue is Harriet’s not Ben’s, and her fears prove justified. She hopes this new doctor might be able to diagnose Ben’s condition, but the specialist, Dr. Gilly, states that the issue lies in the fact that Harriet clearly doesn’t like Ben very much. After some back-and-forth, Harriet asks if the child is human and the doctor seems to entertain the possibility that he is not. Harriet suggests Ben is a throwback from another time, and the doctor says she’s not qualified to determine this and wouldn’t know how to proceed even if she were. Harriet settles for a sedative prescription she can use on Ben in moments of crisis.
At Christmas, the older children decline to return home, spending the holidays with their grandparents instead. Dorothy takes Jane to live with her permanently, they send Paul to a psychiatrist, and David works more and more to pay for these additional financial needs.
John announces he’ll be leaving town to attend school and Ben begs for John to take him with, but this isn’t possible. Ben remains incapable of understanding social dynamics, stories, or games. The family anticipates and fears Ben’s imminent adolescence. The full family returns for the summer holiday in 1986, and Paul asks to be sent to boarding school like the others.
At the end of the holiday Ben moves on to secondary school, bringing home friends: Derek, Billy, Elvis and Vic. Harriet wonders if these boys pity her son, but, in fact, he seems to act as their leader, and the group is the envy of the entire school. Ben and the gang disappear for days at a time and Harriet notices an uptick in crime in the area, wondering if Ben’s gang has something to do with it.
Harriet and David decide to move and David suggests they not tell Ben, who is off with his gang, where they’re going. Harriet gives Ben the address anyway, but he discards it as though he cares little about remaining in contact with her. Harriet watches Ben hanging out with his friends one night, wondering what will become of him, wondering if he has found his tribe in these other boys or if he’ll never find another being with whom he fully identifies.
