Written from the perspective of a third-person limited omniscient narrator, A Monster Calls opens with a monster visiting thirteen-year-old Conor O’Malley, the novel’s protagonist, at seven minutes past midnight on a Sunday night in October. Conor is awake because he has just had a recurring nightmare that features hands slipping from his grasp. He believes he cannot tell anyone about the nightmare, particularly his parents or grandmother. He wishes the nightmare would go away. Conor feels a rush of panic when the monster calls his name. He wonders if his father has made a surprise trip home from America. Out of his bedroom window he sees the moonlit church tower and graveyard. An ancient yew tree grows from the center of the graveyard. A cloud covers the moon.
A moment later, the moon shines on the yew tree again, but it is now in his yard. The upper branches gather into a great and terrible face. With creaking and groaning sounds the rest of the branches take the form of a humanoid shape. The thin leaves weave together into a furry green skin which moves as though the monster is breathing. The monster places its hands on either side of Conor’s window and leans close until its face fills the window frame. In its whooshing breath, the monster says it has come to get Conor. Conor isn’t afraid, because it isn’t the monster he expected. He tells the monster to come and get him then. The monster roars and smashes the house. It picks Conor up and asks if Conor really isn’t afraid. Conor confirms that he isn’t afraid—at least not of this monster. The monster swallows Conor whole.
Conor enters the kitchen while his mother is still in bed and disposes of a plastic bag in the larger garbage can, covering it with other trash so the bag wouldn’t be obvious. He prepares his own breakfast, as he has grown used to doing. As he eats, Conor considers the yew tree outside and assumes the encounter with the monster had been a dream. However, his bedroom floor had been covered in leaves, which he’d disposed of in the plastic bag, assuming the leaves had blown in the open window. Conor’s mother wakes up and thanks him for tidying the kitchen and taking out the trash. Conor notices she isn’t wearing the scarf she uses to cover her bald head, which looks so fragile it hurts his stomach to see it. She informs him that his grandmother is coming to stay in order to help out with things during Conor’s mother’s new round of treatments. Conor is resistant because he has to give up his room and sleep on the settee (i.e. sofa) when she stays. He remembers the bag of leaves and thinks maybe it’s not the worst thing to have her stay in his room.
At school, Conor gets up with blood in his mouth, having bitten his lip when he hit the ground. Harry, Anton and Sully laugh at him. Harry tells him to watch the steps, saying he might fall. The narrator comments that Harry used to be the Blond Wonder Child, and was always the teacher’s pet. But in the past year, since the nightmares started, Harry began picking on Conor, tripping Conor every morning as he came into the school grounds. Today, Lily Andrews tells the boys to leave Conor alone. Harry says that Conor is bleeding. Sully says he’ll have to get his “baldy mother” to kiss it better. Lily pushes Sully into a shrubbery. Miss Kwan, the students’ Head of Year, witnesses the push and scolds Lily. Lily says the boys were making fun of Conor’s mum, but when Miss Kwan asks Conor if this is true, he says it isn’t; he says he fell and the boys were helping him up. Lily’s face shows hurt and surprise as Miss Kwan pulls her away. Harry holds out Conor’s rucksack to him and says, “Well done, O’Malley.”
After school, Conor walks home with a frown. He dreads having to complete Mrs. Marl’s “life writing” assignment, which requires Conor to write about important events in his life. Conor doesn’t want to write about the events he remembers: his father leaving, his cat disappearing, the afternoon his mother told him they needed to have a little talk. Lily catches up to Conor and asks why he let her get into trouble. He gets angry at her for having intervened, claiming he was fine. He says that it wasn’t his fault she got detention—it was hers. He storms off and she shouts that they used to be friends.
The narrator comments that Lily’s and Conor’s mothers were friends before the children were born. Things changed between Conor and Lily after the news about Conor’s mother. Conor will never forgive her for having let the bad news spread to everyone at school. Near his house, Conor walks by the yew tree, which reaches out its arms and says Conor’s name. He steps back so fast he nearly falls. When he looks up, it is just a tree again.
Conor's mother falls asleep watching EastEnders, a British soap opera. The phone rings and Conor lets it go to voicemail when he sees it is Lily’s mother’s calling. While in bed he hears his mother vomiting in the bathroom. He asks if she needs help but she says the treatments mean it is something she is used to by now. At 12:07, Conor looks out his window to see the monster looking in. Conor asks what it wants and the monster says it is not what the monster wants from Conor, but what Conor wants from the monster. Conor goes to the yard and tells himself it is just a dream. He notices he feels no terror though, unlike the other nightmare. The monster says it has had many names over time: Herne the Hunter, Cernunnos, the eternal Green Man. The monster lifts Conor up and says it is everything untamed and untameable.
The monster says it will visit on further nights to tell Conor three tales from when it walked before; Conor will deliver the fourth story, and it will be Conor’s truth. The monster says the truth Conor hides is the thing of which Conor is most afraid. Conor realizes the monster is referring to telling the truth of his nightmare, which he refuses ever to do. The monster threatens to eat Conor alive if he doesn’t tell the truth of his story. After the monster opens its mouth terrifyingly wide, Conor wakes up in bed. He switches on the lamp and sees his floor is covered in poisonous red yew tree berries which have somehow come in through a locked window.
Grandma arrives and asks Conor if he has been a good boy, pinching his cheeks hard. She slaps him on the cheeks and tells him to put the kettle on. She turns to her daughter and asks what they’re going to do with her. The narrator comments that Conor’s grandma is abnormal: she wears pantsuits, dyes her hair in order not to show any grey, and employs a cleaner. She asks about Conor’s school and then suggests he should attend a private school. Conor disapproves of her snobbery.
After eating Chinese takeaway for dinner, Conor is stuffing the foil packets into the trash can when Grandma says she isn’t Conor’s enemy; she is here to help his mother. She wants to talk about what’s going to happen, but Conor angrily tells her his mother will be better tomorrow, because she is always sick after treatments. He sees the monster outside the kitchen window. Grandma says she won’t be better, she’ll only seem better. Grandma says Conor’s mother needs to talk with him about him coming to live with Grandma. The room seems to go dark. Conor says he’ll never live with her. She says she’s sorry, but he is. She says it is important for him to know he has a loving home to go to when this is all over. Their conversation is interrupted when they hear Conor’s mother coughing in the living room. Grandma rushes in to rub Conor’s mother’s back as she throws up into a bucket. Grandma looks at Conor with a hard, unreadable expression.
In the opening chapters of A Monster Calls, Ness establishes the novel’s premise: Conor O’Malley, a thirteen-year-old boy whose mother is battling cancer, is haunted by a nightmare in which something happens that is so troubling he believes he can never let anyone know the dream’s content. In this troubled state, Conor is visited by a monster who transforms from an ancient yew tree planted in the neighboring church’s graveyard.
While the monster’s intimidating presence ought to terrify the young boy, in an instance of situational irony Conor is indifferent to the monster because it is not the monster from his nightmare. Although Conor’s first interaction with the monster ends much in the way his nightmare ends, Conor wakes up to discover his floor is covered in leaves. With this physical evidence, Conor isn’t able to dismiss the visitation as a nightmare. Conor reacts by hiding the leaves in the trash—a symbol for how the monster’s wisdom will stay with Conor in his waking life even as he tries to ignore what the monster tries to impart.
The opening chapters also establish Conor’s isolated life at school. After the news of his mother’s diagnosis circulated, Conor was unable to feel comfortable around people who didn’t know how to behave in his presence. In Conor’s alienated state, the only real attention he receives is from the playground bullies Harry, Sully, and Anton, who assault him every morning on his way into the school grounds. While Lily steps in to defend him, Conor resists her assistance. In an instance of situational irony, Conor lets Lily get in trouble instead of the students who harass him. His animosity toward Lily is explained when the narrator comments on how Conor still holds Lily responsible for having told everyone at school about his dying mother.
During the monster’s second visit, the monster says it has come to tell Conor three tales, after which Conor must tell the truth of his nightmare. Conor resists accepting the monster’s premise, but over time the monster will lead Conor to stop denying the truth of his nightmare and his mother’s cancer.
In addition to the antagonists of Harry, Lily, Miss Kwan, and the monster, Ness introduces in the opening chapters the antagonizing figure of Conor’s grandmother. Conor is quick to anger in her presence, in large part because she attempts to discuss in realistic terms what life will be like after Conor’s mother dies. Because Conor believes it is his responsibility to hold out hope for his mother’s survival, he is unable to engage in conversations that would require accepting her eventual death. He uses anger as a means of signaling to his grandmother that he is unwilling to discuss his mother’s death. His grandmother is also feeling anger as a result of the grieving process, and so she responds sternly that he will come to live with her. Their argument is interrupted by the sound of Conor’s mother coughing and vomiting in the sitting room, suggesting that as unpleasant as his grandmother’s perspective may be, she is right to be pessimistic.