The Watsons are a black family living in Flint, Michigan. The mother, Wilona, is from Birmingham, Alabama, but moved to Flint when she married Daniel, the father. Their three children are Byron, who is 13; Kenny, who is 10; and Joetta or "Joey," who is 5. Kenny is the protagonist of the story; he is very smart and relatively quiet. Byron is something of a juvenile delinquent and possesses a knack for breaking the rules, and Joey is a sensitive child and a strict rule-follower.
It is the dead of winter in Flint, and naturally it is extremely cold. Wilona misses the South for its warmth, but Daniel reminds her of the way African Americans are treated in places like Birmingham. (It is 1963, the height of the Civil Rights Era.) When Byron and Kenny are sent outside to scrape ice off the car, Byron's lips freeze and adhere to the rear view mirror as he attempts to kiss his reflection, and he must be yanked off.
The Watson children go to school at Clark Elementary; Byron is still there because he was held back a grade or two. Yet Byron is king of the school, so Kenny does not get teased as much as he would if he were not Byron's brother. When he does get teased, though, it is either because of his lazy eye or because he is a bit of a teacher's pet. Because he is so smart, other students call him "Poindexter." Usually, a bully named Larry Dunn is the one who gives him trouble.
One day, though, two new kids come to school; they are Rufus and Cody, who moved from the South. Because of their accents and the state of their clothes (they are poor, so they share clothes often), they immediately become targets for the jeers of other students. Kenny, however, becomes fast friends with Rufus, and the two boys often play with Kenny's favorite dinosaur figurines together. Their friendship is put in jeopardy when Kenny laughs after some bullies make fun of Rufus's clothes, though soon Kenny realizes he is wrong and apologizes.
Byron's antics continue, and his misbehavior grows even worse. He manages to convince his little sister that the reason people in their area have to dress so warmly is because garbage trucks come and pick up frozen, dead people in the street every morning; people with Southern blood like the Watsons' freeze faster. When Larry Dunn steals Kenny's good leather gloves, Byron gives him such a terrible beating that Kenny even feels bad for the bully. Byron gets in big trouble for playing with matches, for signing his name for groceries at the store and not telling his parents, and for letting his partner in crime, Buphead, administer a chemical straightening treatment to his hair.
The Watson parents decide that something must be done about Byron. They fix up their old car, equip it with a new record player, and decide that they will take a road trip down to Birmingham to leave Byron to spend the summer with strict Grandma Sands. Byron is not happy about this. Wilona plans the entire trip out to the last detail, including where they will stop to spend the night on the road, but once they get started it becomes clear that Daniel's plan is to drive straight through to Alabama without stopping once.
The Watsons make it to Grandma Sands's house, and Kenny is surprised to see that Grandma Sands is just a little old lady. Things are different down in Alabama, starting with the heat, which is unbearable. Byron does not seem inclined to perform his usual antics, and Kenny believes that his brother has given up fighting against authority. One day the two boys go swimming in the lake, and Kenny goes off to a forbidden area by himself and gets stuck in a whirlpool. He almost drowns before Byron pulls him out and saves him.
Joey goes off to Sunday school on a normal morning, but later on the Watsons are informed that the church she went to was bombed by white supremacists. Four innocent little girls died; Kenny follows behind his family to the church and thinks he sees Joey dead, too, but she shows up at Grandma Sands's house alive. She says she saw Kenny laughing and beckoning her away from the church before she went in, so she followed. Kenny has no idea what she is talking about.
Even after the family gets back to Flint, Kenny is traumatized by the bombing and its aftermath for a long time, and refuses to talk to anyone about it. Finally he has a long conversation with Byron, who tells him that the world is not fair, since there are people in it who let hate consume them and turn them into monsters. He tells Kenny to snap out of it, and that he is going to be okay. After crying for a while, Kenny finally realizes that Byron is right. Everything is going to be fine, so long as he has his family around him.