Damon Fields tells the story of his life from birth to adulthood. Damon was born in Lee County, which is located in the Appalachian region of Virginia. His nickname, Demon Copperhead, is a play on “Damon.” Copperhead comes from his father’s nickname, and it’s also a reference to Demon’s red hair.
Demon and his mom live in a trailer owned by the Peggots, who live next door. Matthew Peggot, whom everyone calls Maggot, is around Demon’s age and is Demon’s best friend,. Demon is often in and out of the Peggot house, and the Peggots serve as a kind of surrogate family for Demon.
When Demon is a boy, Demon’s mother becomes involved with a man named Stoner. Stoner is vituperative, strict, and abusive to both Mom and Demon. He tells Demon he can’t spend time with Maggot because he suspects Maggot is gay. Whenever Stoner is around, Mom seems to shrink into the background. One day Mom overdoses on painkillers, and Demon is assigned a caseworker from the Department of Social Services (DSS), Miss Barks. Unable to live with Mom while she’s in recovery, Miss Barks finds Demon a temporary foster care placement at a farm belonging to a man named Mr. Crickson. At Crickson’s farm, Demon lives with Mr. Crickson’s other foster children, Tommy and Fast Forward. Tommy is kind and caring, while Fast Forward is the larger-than-life quarterback of the high school football team. Crickson takes the boys out of school to do manual labor on the farm.
On Demon’s eleventh birthday, Miss Barks calls him and tells him that his mom has died of an overdose. Demon doesn’t know whether her death was a suicide or an accident. He also doesn’t know where he’s going to live now that Mom has died. That Christmas, he accompanies the Peggots to nearby Knoxville. In Knoxville, Demon sees Aunt June who has adopted her niece, Emmy, after Emmy’s dad died. Emmy and Demon spend many nights staying up late and commiserating.
When Demon returns to Lee County, Miss Barks finds him a new foster family, the McCobbs. Mr. McCobb insists that Demon pay rent, even though the state pays the McCobbs for fostering him, and even though Demon is just a child. He finds Demon a job in a makeshift dump behind a convenience store and orders Damon to pick through the trash pile to find things they might be able to sell. Damon is also tasked with draining the acid from batteries. After a while, he begins to suspect that he might be working for a meth lab. At school, Demon the other kids make fun of Damon for being poor. Damon’s time with the McCobbs ends when the McCobbs, facing financial difficulties, decide to move to Ohio to be with Mrs. McCobb’s family.
Facing more uncertainty about his future, Demon decides to track down the remaining family that he’s aware of. He hitchhikes to Murder Valley, Tennessee, to find his paternal grandmother, Betsy Woodall, whom he only knows through the stories Mom would tell. When he arrives, he discovers that Betsy has taken in and raised 11 girls—only girls—through the years, and that she lives with her brother, Mr. Dick. Betsy decides to try and help Demon find a better foster placement. She remembers that one of the girls she raised married someone in Lee County before she died. Betsy makes the necessary calls and then Demon goes back to Lee County to live with Coach Winfield and Coach Winfield’s daughter, Angus.
In Lee County, Demon’s life takes a turn for the better. Demon gets along with Coach Winfield and Angus. He excels at school and is eventually enrolled in the gifted and talented program. He also starts taking lessons from the art teacher at the local high school, who encourages him to pursue his passion for drawing.
Coach Winfield also takes an interest in Demon’s football ability, thinking that he’ll make a good tight end. The summer after eighth grade, Demon goes to summer football training camp, and when he enters high school, he quickly becomes a star on the team. Coach Winfield’s assistant, U-Haul, seems strangely jealous of Demon and corners him one night to tell him that he’s not really family to Coach Winfield or Angus and that he shouldn’t get too comfortable in their home.
Around this time, Demon reconnects with Fast Forward, and the two begin to spend more time together. However, Demon starts to suspect that there might be something a little sinister about Fast Forward that he didn’t notice when he first met him.
In October of his sophomore year, Demon injures his knee during a football game. A doctor named Dr. Watts comes to see him and writes him a prescription for Lortab, an opioid. Demon starts playing football again four weeks later, but he’s on a heavy regiment of painkillers by then. When he tries to wean himself off the painkillers, he experiences symptoms of withdrawal that seem even worse than the pain itself. Around this time, Demon meets Dori and falls in love with her almost instantly. He’s surprised when, on their first date, she gets high on fentanyl—and shares some with Demon.
When football season ends, Coach tells Demon that it’s time to get off the painkillers. Demon tries, but he keeps experiencing withdrawal symptoms. He and Dori continue to do drugs together, including pills, and Demon also begins smoking heroin. Around this time, Demon reconnects with Tommy, who is working at a local newspaper. Tommy remembers the comics Demon used to draw, and the two begin working on a weekly comic strip together for the local paper. Emmy, meanwhile, leaves her long-time love interest, Hammer, to run away with Fast Forward.
Dori’s dad, who has been battling cancer, dies that winter, and Demon isn’t sure if Dori will ever recover from her grief. Demon feels like he’s overstayed his welcome at the Winfield’s house, so when Dori asks him to live with her, he accepts. Dori begins doing fentanyl and heroin more often, and Demon comes home to find her overdosing at least five times. When Dori becomes pregnant, Demon hopes that it might provide Dori with the motivation she needs to stay sober, but Dori continues to struggle with addiction and later loses the baby.
Sometime later, U-Haul tries to blackmail Angus into having sex with him. He accuses Coach Winfield of embezzling funds meant for the football team and threatens to expose the supposed illegal activity. When Demon goes to help Angus, she tells him that U-Haul has overseen bookkeeping for years and has been putting some of the football team’s money into his mother’s bank account each month.
One afternoon in April, Demon returns home and discovers that Dori has died of an overdose With nowhere else to go, Demon lives out of Dori’s old car. When he’s with Maggot one day, they see Hammer with a flat tire on the side of the road. They pick him up, and Hammer grabs his rifle from his car. When Hammer hears that Fast Forward is at Devil’s Bathtub, a waterfall outside of town, Hammer orders Demon and Maggot to drive him there so he can confront Fast Forward about stealing Emmy from him and then treating her poorly. They agree. At the waterfall, Hammer and Fast Forward get into a violent altercation. When Hammer threatens Fast Forward with his rifle, Fast Forward dives from the cliff but slips and lands on the rocks. He dies on impact. Hammer dives into the water to try to save Fast Forward, but the current sweeps him away, and he drowns.
Because he gave Hammer drugs, Maggot ends up being charged as an accessory to his death and goes to juvenile detention. Aunt June tells Demon that she’ll help put him through rehab, and Demon moves to Knoxville to enter rehab and get sober. After three years away, Demon returns to Lee County. He reconnects with Angus, who he realizes might have feelings for him. As they drive together to see the ocean, which Demon has always wanted to see, he thinks that he might have feelings for Angus, too.