The narrative of "The Man Child" centers around Eric, an eight-year-old boy who lives on a large farm with his mother and father and in the frequent company of their neighbor, his father's best friend Jamie. Jamie and Eric's father were in the war together, and now that they are both home, back to the land their fathers farmed as neighbors before them, they spend many nights together at a bar called The Rafters. The main scene of the story takes place as Eric's mother and father are hosting Jaime's birthday dinner. In attendance are Eric, Eric's parents, Jamie, and his old dog.
The story begins as Eric returns home from a day of exploring and playing on his father's land. Dinner that night will be in honor of Jamie, who is turning thirty-four. Though Jamie is two years older than Eric's father, he is accused by Eric's parents of acting younger than his age and pitying himself like a child. As Eric wanders his way home, he thinks about his parents, and especially his mother, who has seemed so much older to him since she fell ill and had to go away for a while. When she went away, she was pregnant, and when she returned, there was no baby. Eric has another baby sister "in the churchyard" whose "name would have been Sophie." He rushes home because the sun is falling fast, and his mother would be angry if he were caught in the dark in the fields. She doesn't like letting him go out in the first place, but his father encourages his curiosity and exploration of the land that would someday belong to him.
Eric eats his dinner quickly and falls asleep on his mother's lap before they even cut the cake. The sun is still shining on their little party, and even after Eric wakes up, he keeps his eyes closed. The adults' conversation is tense and charged with subtextual emotions. Eric's father bullies Jamie about how he doesn't have a family, and how he wasn't able to hold on to his wife. Jamie denigrates his ex-wife, and both Jamie and Eric's father suggest she was promiscuous. Eric's mother defends Jamie's ex, saying she was beautiful, and he never paid enough attention to her. The night wears on and so does the conversation. Jamie alludes to having knowledge of some shameful secret he and Eric's father share that Eric's mother knows nothing about and about which she has no desire to know. Eric's father playfully slaps Jamie on the knee, and Jamie, now drunk, jumps up and yells, knocking his chair over.
After his outburst, Eric's father instructs his wife to make some coffee for Jaime while he takes Eric for a walk. On their walk, Eric's father takes them to the borders of their land and tells Eric that all this land is his. It belongs to him, and when he has children, the land will belong to them, too. Eric is surprised by the vastness of his own domain. He asks his father whether Jamie has any land, and his father tells him no, he doesn't, because he lost his land. Eric's father bought Jamie's land from him, claiming to have given him a better price for it than anyone else would have.
At the time of Jamie's birthday, Eric's mother was pregnant again. By the end of the summer, a few months after the party, she falls ill again and has to be taken away, likely to some in-patient medical facility. During her time away, Jamie spends most nights at Eric's house. It's strongly suggested that Jamie and Eric's father have a romantic relationship that started long ago and continues throughout the narrative. When Eric's mom returns, she returns without a child.
The story concludes on a night after Eric's mother's return from her time away. Eric has spent his day exploring the land and thinks, as he hoses himself down for dinner, about what he'll explore the next day. He's taken to proudly surveying the land like he's watched his father do so many times in the past. As Eric is getting ready outside, Jamie approaches him. He tells him that he and his father want to show him something in the barn. When Jamie brings Eric to the barn, his father isn't there. It's just the two of them. Eric asks where his father is, and Jamie tells him he's probably at The Rafters. Jamie puts his hand over Eric's mouth and Eric realizes that he's in danger. Eric pleads for his life. He bargains with Jamie. He tells him that he can have all the land. He tells him that if he kills his dad, he'll be his little boy. But Jamie says he doesn't want the land. He strangles Eric, breaking his neck. He then returns to his home, collects his dog, and leaves.
"The Man Child" explores themes of family, sexuality, propriety, and property in a rather short, self-contained narrative. By centering the narrative on Eric and tracking Eric's eight-year-old perspective, much of the subtext surrounding Jamie and Eric's father's relationship is left entirely to the reader and to Eric's unsuspecting observations. His age lends a naivety to the story which justifies Eric and his father's discussion of the land, and how the land is passed from father to son, which is something that Eric would surely have known if he were older. The fact that Eric's mother cannot seem to bring another child to term means that Eric is the sole inheritor of his father's land, and any chance of his father's legacy living on in the way he plans for it to depends on Eric.
There are many subtle clues that lead the reader to the possible conclusion that Jamie and Eric's father are involved in a romantic relationship. During Jamie's birthday dinner, Jamie says that he's not too old to still do all the things he and Eric's father used to do together. He then asks Eric's mother if he's ever told her about the things they used to do together. The "things" to which he's referring are left ambiguous, and Eric's mom says she'd rather not know. Eric's father then chimes in, saying, "He wouldn't tell you anyways ... He knows what I'd do to him if he did." Later on, when Eric's mom leaves to receive medical attention, Jamie spends every night at their house. He sleeps there, and Eric can hear his feet pattering around his parents' room. Then, finally, in the concluding scene, Jamie outright tells Eric that he loves his father. Of course, this doesn't have to mean romantic love, but it would make sense given his actions, and given Eric's mother's attitude toward Jamie when she returns from her most recent leave of absence.
For Jamie, Eric represents everything he can't give to Eric's father, the man he loves. They can never be together because they can't make a family together and contribute to the land and Eric's father's legacy. And since he can't give that to him, he wants to take it away from him, which is why he kills Eric. Eric's mother becomes less of a threat to Jamie because she cannot bear children. Eric's mother's coldness toward Jamie seems to stem from this knowledge that her ability to provide a family to Eric's father seems to be her significant edge over Jamie in the competition for Eric's father's love and attention. Her protectiveness of Eric can also be understood in this light—Eric is her link to Eric's father; especially now that she's realizing another child is unlikely for them, Eric is their only chance at continuing a family line.