Caelum Quirk, a middle-aged high school English teacher, narrates the story of his life before and after the April 20, 1999, massacre at Columbine High School in Littleton, Colorado, where he and his third wife, Maureen, both work. The novel traces how the shooting and its aftershocks ripple through their marriage, Maureen's mental health, and Caelum's understanding of his tangled family history on the Quirk farm in Three Rivers, Connecticut.
Caelum opens by recalling a mundane encounter with Eric Harris and Dylan Klebold at a pizza shop on April 16, four days before the shooting. That same night, he ignores Maureen's lit-candle signal for intimacy, a gesture devised during couples counseling after her affair with Paul Hay. In flashback, Caelum recounts discovering the affair, attacking Hay with a pipe wrench, his arrest and anger management classes, and the couple's eventual reconciliation through therapy with Dr. Beena Patel. They relocated to Colorado for a fresh start, both taking jobs at Columbine.
Before the shooting, Caelum mentors Velvet Hoon, a volatile sixteen-year-old emancipated minor with a history of abuse and foster care. Velvet shows genuine writing talent, producing a prize-winning essay called "Hope Cemetery" about her grandfather's sculptures in Barre, Vermont. She sabotages the award ceremony, however, and later offers Caelum a sexual favor, a disclosure he hides from Maureen. Their mentoring relationship collapses, though Velvet maintains a bond with Maureen, who serves as a maternal figure.
On April 17, Caelum learns his Aunt Lolly, his surrogate parent and a longtime corrections officer at the Bride Lake State Farm for Women, has had a stroke. He flies to Connecticut, leaving Maureen behind. Flashbacks reveal Caelum's childhood on the farm adjacent to the women's prison: his alcoholic father, Alden Quirk III; his devout mother, Rosemary; and his terrorization by a school janitor. The boy secretly steals food for his trespassing father and an unnamed "kerchief lady" who hide in the farm's corn maze, letting an innocent prisoner take the blame.
Caelum visits Lolly at the hospital and combs her hair, though she does not recognize him. She dies overnight from a second stroke. While he makes funeral arrangements at the farmhouse, the Columbine shooting unfolds on television. Unable to reach Maureen, he flies back to Colorado and finds her at Leawood Elementary School, the family reunion site, traumatized but alive. Velvet had come to the school that morning to discuss reenrollment and was in the library when the shooters entered. Maureen hid in a break room cabinet for hours, listening to gunfire, reciting the Hail Mary, and writing Caelum a farewell note on the cabinet wall. The district attorney confirms that Velvet escaped the library alive.
The aftermath consumes their lives. Caelum attends the victims' funerals and a massive public memorial. At a grief counseling session organized by Pastor Pete Kromie, Dr. Bethany Cake discusses PTSD and the risk of symptoms becoming chronic. Maureen develops severe posttraumatic stress disorder: flashbacks, hypervigilance, insomnia, weight loss, chronic pain, and paranoia. She is prescribed Xanax and Restoril but quickly begins overusing them. At the end of the school year, Caelum sells the house, and the couple drives back to Three Rivers.
In Connecticut, Maureen cycles through therapists, rejecting each. Her hair falls out, and she has pain that doctors call psychosomatic. Caelum cobbles together income from adjunct teaching at Oceanside Community College, night-baking at his friend Alphonse Buzzi's bakery, and sawmill work. When Maureen is caught obtaining tranquilizers from multiple doctors, Captain Jerry Martineau, Caelum's former high school track teammate, intervenes without arresting her, requiring her to attend NarcAnon, a narcotics-recovery support group, and resume counseling. She begins therapy with Dr. Patel, makes gradual progress, and eventually returns to work as a third-shift nurse at Rivercrest Nursing Home.
On New Year's Eve 2003, a series of crises during her shift, including a drunk intruder who gropes her and triggers a Columbine flashback, causes Maureen to inject herself with a patient's leftover Xanax. This secret relapse continues for months. On October 9, 2004, driving home from her overnight shift, she strikes and kills seventeen-year-old Morgan Seaberry as he crosses a road. Investigation reveals she was driving under the influence. Attorney Lena LoVecchio negotiates an Alford plea, in which a defendant accepts punishment while maintaining innocence. At sentencing, Morgan's mother demands the maximum penalty, and the judge imposes five full years. Velvet bursts into the courtroom shouting support as Maureen is led away to Quirk Correctional Institution, the prison named after Caelum's great-grandmother, Lydia Quirk.
Caelum visits Maureen regularly. Hurricane Katrina refugees Moses and Janis Mick arrive at Alphonse's bakery, and Caelum rents them the farmhouse's upstairs. Janis, a Tulane Ph.D. candidate in Women's Studies, discovers documents Lolly had removed from the prison. These include diaries kept by Lydia and letters from Lydia's grandmother, Elizabeth Hutchinson Popper, a 19th-century abolitionist, Civil War nurse, and advocate for incarcerated women. Janis writes a paper tracing Lizzy Popper's decades-long campaign for a separate women's reformatory, a dream Lydia realized as superintendent of the Bride Lake facility in 1913. The archives also reveal that Lizzy's brother Roswell likely abused Pansy, the illegitimate daughter of Lizzy's dead husband, who ran away and died at 15 in a New York prison.
Among these materials, Janis finds clippings that lead Caelum to discover his birth mother was not Rosemary but Mary Agnes Dank, the "kerchief lady" from the corn maze. A second birth certificate confirms this, and a DNA test establishes that Alden Quirk III was indeed Caelum's biological father.
In Caelum's Quest in Literature course at Oceanside, Iraq War veteran Kareem Kendricks, who lost his right hand to a roadside bomb and has PTSD, grows increasingly agitated. After confiding his domestic troubles to Caelum, Kendricks shoots his estranged wife (who survives) and a social worker, then kills himself. Caelum is haunted by the thought that he might have intervened.
Ulysses Pappanikou, an old friend of Caelum's father, helps Caelum unearth a footlocker beneath the farm's old apple house containing two infant remains. Ulysses reveals that he and Caelum's father buried the trunk in 1953. Alden had discovered a mummified baby in a hidden attic crawl space as a boy and later placed beside it a stillborn son that Mary Agnes delivered after a self-induced abortion, the child fathered by African American baseball player Calvin Sparks. Caelum and Maureen deduce that the mummified infant was likely Pansy's child, linking the family's darkest secrets across generations.
Father Ralph Brazicki, Caelum's former track teammate and now the prison chaplain, organizes a family Mass at Quirk CI. Caelum and Velvet attend. After the service, Maureen collapses with a sudden headache and dies of a cerebral aneurysm in the ambulance while Caelum, barred by security protocol from riding with her, follows in his car.
Caelum withdraws into grief and alcohol but gradually re-engages with life, teaching creative writing and GED English at Quirk CI. He loses the civil suit filed by the Seaberry family and surrenders the farm, moving into a riverside condo. Morgan's brother, Jesse Seaberry, who has been dating Velvet, becomes Caelum's Alcoholics Anonymous (AA) sponsor. Velvet becomes pregnant with Jesse's child. She and Caelum travel to Hope Cemetery in Barre, Vermont, where Caelum finds a granite Pandora sculpture by Velvet's grandfather, its jar containing a carved infant labeled "hope." Velvet tells Caelum they plan to name the baby Caelum Morgan Seaberry and calls him "Grandpa." When he places his hand on her belly and feels the baby kick, he experiences the simultaneous pull of the past and the promise of the future, recognizing the moment as the hour he first believed.