Set in early 1980s England against a backdrop of racial tension and social unrest, the novel follows Leon, a mixed-race boy, from the age of eight through ten as he loses his family, enters the foster care system, and fights to hold on to his baby brother.
In April 1980, Leon holds his newborn half brother for the first time at the hospital. His mother, Carol, is white; his father, Byron, is Black and largely absent. The baby, whom Carol names Jake, has a different father, a man named Tony. Leon is devoted to Jake from the start, whispering to the sleeping infant about their family.
Back at their housing estate, Carol's condition deteriorates. She cries constantly, stays in bed for days, and leaves Leon and Jake with her friend Tina. When Tony appears at their door, he tells Carol bluntly that he does not want another child or girlfriend and leaves. Carol apologizes to Leon the next day, begs him to look after Jake and get an education, then retreats to bed.
Leon stays home from school to care for Jake, developing a routine of diaper changes, bottle-making, and feeding. Carol stops getting up entirely, lying unresponsive in soiled sheets. When Leon runs out of food, diapers, and money, he goes to Tina for help. Tina follows him home, discovers the crisis, and calls an ambulance and Social Services.
A social worker Leon calls "the Zebra" because of her black-and-white striped hair takes both children to a foster home run by Maureen, a large, warmhearted, red-haired woman. Maureen feeds Leon enormous meals and asks him to describe Jake's routine, treating Leon as the expert on his brother. For the first time in months, Leon is well-fed, bathed, and safe.
The stability shatters when a social worker named Salma explains that Jake, as a young white baby, will be adopted. Leon will not go with him. Maureen tells Leon the reason is race: People want white babies and Leon is not white. When the couple arrives, Leon uncurls Jake's fist, kisses it, and gives him his yellow truck. After Jake is taken, Leon destroys his bedroom, singing Jake's baby songs until the rage empties from him. Maureen does not scold him. She places a photograph of the brothers by his bed and gives him Jake's Big Red Bear.
Maureen wakes Leon one night as he grinds his teeth and promises he will see Jake again, repeating it until he believes her. Leon reads part of Carol's file from Salma's bag and learns of his mother's "emotionally unstable personality disorder," her dependence on prescription drugs and alcohol, and her failure to attend scheduled supervised visits with her children.
Carol visits once, gaunt and shaking, with stained teeth and a new boyfriend. She sees the photograph of Jake and collapses on the floor. Maureen refuses to let her take it, but Leon runs after his mother and presses the photograph into her hands. She holds it against her heart and drives away.
When Maureen is hospitalized, Leon calls 999 and saves her life. He is placed with Maureen's sister, Sylvia. The Zebra brings him a secondhand BMX bike, and riding becomes his one freedom. At a supervised visit, Leon sees Carol, thinner than ever. When they are alone, he imitates Jake's baby noises and tells her he could be Jake for her. They hold each other in grief.
An Independent Reviewing Officer named Mike tells Leon that adoption is permanent and Jake lives far away. Afterward, Leon destroys Sylvia's bathroom, ripping the toilet seat off its hinges. Sylvia does not throw him out. She makes him clean the mess and tells him not to ruin a good home when life deals bad news.
Leon discovers the Rookery Road Allotments, a community garden behind iron railings, and befriends two men. Tufty Burrows is a Black man who works at a bike shop and writes poetry. Mr. Devlin is a gruff Irishman who keeps a brick shed at the allotments filled with carved wooden heads. Tufty teaches Leon to plant seeds and care for seedlings. Mr. Devlin reveals that the carvings depict boys from a school he ran in São Paulo, Brazil, and four portray his own son, Pedro Gabriel, who died as a child. He gives Leon a quarter-plot of land for his tenth birthday.
Leon meets Tufty's friends, including Castro, a political activist. When plainclothes police enter the allotment searching for a protest leader, they taunt Tufty and Castro with racist language, drag Castro away, and ransack Tufty's shed. Leon secretly stocks an abandoned shed with canned food, a blanket, and stolen items: Mr. Devlin's wooden pistol, which Leon believes is real, a carved head of Pedro Gabriel, and a pruning knife. On his birthday, he receives a photograph of Jake from the adoptive family and memorizes the address on the back: 287 Dovedale Road.
When Maureen returns from the hospital and moves in with Sylvia, Leon overhears the sisters discussing retirement and interprets their plans as proof that no one wants him. That night, as riots erupt following Castro's death in police custody, Leon climbs out of Sylvia's window and rides into the burning streets, determined to reach Dovedale Road, take Jake, and find Carol in Bristol.
At the allotments, Tufty and Mr. Devlin discover Leon in his shed. The stolen carving of Mr. Devlin's son falls from Leon's backpack, and Mr. Devlin is anguished. Leon pulls the pruning knife and slashes the air, screaming that no one cares about him or his brother. He runs into the riot.
Lost between crowds and riot police, Leon pulls the wooden gun and demands directions to Dovedale Road. Mr. Devlin runs forward, shouting the gun is not real, and is struck down. A policeman beats Tufty, then raises his baton at Leon. Leon opens his arms and recites words Tufty taught him: "We are not a warrior. We have dignity and worth." The policeman lowers his arm. Leon rouses Tufty, and together they drag Mr. Devlin to Sylvia's house.
Days later, Maureen takes Leon by train to Bristol. Carol tells him directly that she cannot look after him. Before she leaves, Leon asks if she still loves Jake. She whispers, "And you. I still love you," gives a small curtsy, and is gone.
On the train home, Maureen reveals she has arranged with Social Services for Leon to stay with her permanently. She is not retiring or getting a dog. She asks for two promises: that Leon tell her when something is wrong, and that he never run away again. Leon agrees.
On the day of the Royal Wedding, Leon, Tufty, and Mr. Devlin set up a party at the allotments. Leon walks to his quarter-plot, where his Scarlet Emperor beans have grown tall with tiny pods. He cracks open a pod and holds a black seed to the sun. It glistens like the center of Jake's eyes. Remembering Maureen's promise that Jake has not gone forever, he plants his Take-A-Chance seeds, mystery seeds Tufty gave him long ago. He covers them with soil, planning to water them and hope for the best. Maureen calls his name. Leon turns and runs toward her.