Inside the O'briens

Joe O'Brien is a 36-year-old Boston police officer living with his wife, Rosie, and their four children in a triple-decker house in Charlestown, a tight-knit Irish Catholic neighborhood. In an opening scene set seven years before the main narrative, Joe flies into an inexplicable rage when he cannot find his service weapon, hurling a cast-iron skillet across the kitchen and smashing a hole in the wall near his youngest daughter Katie's head. In the bathroom mirror, he recognizes the same wild look he saw in his mother's eyes when she was dying in a psychiatric ward. His mother, Ruth O'Brien, supposedly drank herself to death.

Seven years later, Joe is 43 and his children are adults: JJ, the oldest, is a firefighter married to Colleen, a physical therapist; Patrick bartends at a local bar; Meghan dances for the Boston Ballet; and Katie teaches yoga. Troubling signs accumulate. Joe falls on park stairs for no reason. He drops a crystal pitcher at supper, his hand releasing it involuntarily. A routine police report takes him hours. During crowd-control drills, his shoulders shrug and feet shift without his permission, disrupting the entire formation.

Joe's closest friend on the force, Tommy Vitale, grows concerned enough to have his wife, Amy, call Rosie, relaying that Tommy suspects Joe has a drinking or drug problem. Rosie insists Joe see a doctor. At Massachusetts General Hospital, neurologist Dr. Cheryl Hagler observes Joe struggling with simple motor tasks and raises the possibility of Huntington's disease (HD), an inherited neurodegenerative condition that progressively destroys motor control, cognition, and emotional regulation, with no cure. Two months later, she confirms the diagnosis. The disease is always fatal, typically within 10 to 20 years. Most devastating, each of Joe's four children has a 50 percent chance of carrying the genetic mutation. Joe realizes his mother did not drink herself to death; Ruth O'Brien died of Huntington's, misdiagnosed and misunderstood.

That afternoon, Joe sits alone in the Navy Yard with a bottle of whiskey and flips four quarters, one for each child. The first three land on heads. He cannot flip the fourth, for Katie, and pockets it. Two months later, Joe and Rosie gather the children at Sunday supper to deliver the news. Joe explains his diagnosis and that each of them is at risk before breaking down. Colleen, who has encountered HD patients in her work, storms upstairs in tears. JJ reveals Colleen is 10 weeks pregnant, too late for preimplantation genetic testing, a procedure that screens embryos during in vitro fertilization to prevent passing on genetic mutations.

The narrative shifts to Katie's perspective. She has been secretly dating Felix Martin, a Black man from the Bronx who works for a biofuel company. Felix defies every expectation her Irish Catholic family holds for a partner, and Katie fears that once he sees the full reality of her modest life, he will stop loving her. JJ is the first sibling to seek genetic testing, driven by Colleen's pregnancy. His result comes back positive. Patrick refuses to be tested. Meghan is torn. Katie says maybe.

Katie begins genetic counseling with Eric Clarkson at MGH. A preliminary neurological exam reveals no current symptoms, giving her enormous relief. Eric helps her examine what knowing her status would mean, pointing out that being negative while siblings are positive carries its own emotional weight. Felix tells Katie he loves her and asks her to move to Portland, Oregon, where his company is expanding. Katie realizes she must tell Felix about HD first; he takes the news better than expected.

After her blood draw, Katie learns that Meghan is also gene positive, carrying 47 CAG repeats, a count of a repeated DNA sequence on chromosome 4 that confirms the HD mutation. Katie spirals, retreating to her bedroom to black out every inspirational quote on her walls and scrawl Meghan's count above her headboard. She spends three days in bed at Felix's apartment. When she returns, Meghan has repainted the room blue and rewritten every quote in her own handwriting, adding new ones. The sisters embrace and reconcile after years of distance.

Joe's symptoms worsen steadily. He loses weight from constant involuntary movement, drinks from a plastic cup because he shatters glasses, and erupts in rages he cannot control. He is pulled off crossing-guard duty after 911 calls report a drunk officer directing traffic. His chorea, the involuntary jerking movements characteristic of HD, is visible to everyone around him. Joe confesses his diagnosis to his supervisor, quits the force, and has his driver's license revoked.

After the family dog is euthanized and Joe watches news of a shooting at Colleen's workplace, he takes a sledgehammer to the walls of his home in a blind rage. Alone in the destroyed bedroom, he holds his personal handgun. Rosie finds him and refuses to leave, telling him whatever he plans to do, he will have to do it in front of her. Days later, Katie confronts Joe, finding him drinking beer in the dark before noon. She tells him he is the only example she and her siblings have for how to live and die with HD; whatever he does, that is the lesson he is teaching them. Joe breaks down and asks Katie to take him to her yoga studio.

This marks a turning point. Joe begins practicing yoga with Katie, joins a clinical trial, and starts praying alone at St. Francis Church each morning. In yoga, he discovers moments of stillness where his chorea temporarily ceases, shifting his philosophy from "Stay in the Fight" to "Stay in the Pose." During Savasana, a resting pose also called Dead Man's Pose, he relives a memory of his mother in the hospital and recognizes for the first time that her guttural sounds were expressions of love. He weeps, forgives her and himself, and resolves to pass that understanding to his children.

Joe and Rosie's lawyer informs them that Joe's disability pension will be consumed by nursing-home costs unless they legally divorce. Rosie is horrified, but Joe insists it is just paper and holds up his wedding band. She agrees in tears. Joe initially asks Katie to stay in Charlestown to protect Rosie from more loss, but later reverses himself, telling Katie life is too short for regrets. He gives her the quarter he has carried since St. Patrick's Day, the coin he could not flip for her; she throws it into a fountain, making a wish.

Patrick's secret emerges at supper: He has gotten a girl pregnant and refuses to take the genetic test or marry her. Rosie reaches her own breaking point, packing up every religious item in the house and declaring she no longer believes in God. Joe tells her he has been praying at church daily and proposes they divide the burden: He will pray for her and the children, and she will pray just for him.

Baby Joseph Francis O'Brien III is born. Joe declines to hold his grandson, afraid his involuntary movements might hurt the child, but he recognizes the birth as proof that a life with HD holds extraordinary meaning. Meghan announces she has been accepted to a dance company in London. The family's third-floor apartment must be rented for income, meaning Katie must move out regardless.

In the final chapter, the entire O'Brien family accompanies Katie to the genetic counseling clinic for her results. She has packed for Portland and gotten two tattoos: a white feather for hope and a pink lotus flower. She reflects that whether positive or negative, love remains her reason for living, and HD does not change that. Eric holds the sealed envelope and asks if she is ready. Katie squeezes Felix's hand and says, "I am." The novel ends without revealing her result.