The tenth book in the Will Trent series, the novel alternates between two timelines: the present day in Atlanta, where Georgia Bureau of Investigation (GBI) special agent Will Trent and medical examiner Sara Linton investigate a possible serial killer, and flashbacks to eight years earlier in the small Georgia community of Grant County, where Sara's late husband, Police Chief Jeffrey Tolliver, investigated a string of brutal attacks on young women.
The story opens with Beckey Caterino, a college freshman at Grant Tech in Grant County, storming out of her dorm before dawn after a fight with her roommates. She notices that her late mother's tortoiseshell hair clip, a treasured keepsake, is missing from her nightstand. While running through the woods near campus, a man calls her name. She turns, stumbles, and in the moment before she loses consciousness, realizes a hammer is lodged in her skull.
In the present day, Will and his partner Faith Mitchell arrive at Phillips State Prison to investigate a murder committed during a riot. Will's girlfriend Sara is already on-site processing the crime scene. Will is privately anxious about their relationship: Six weeks earlier, he attempted a clumsy marriage proposal, and Sara responded with anger, imposing a moratorium on the topic that has lingered ever since.
During suspect interviews, an inmate named Daryl Nesbitt passes a note offering to trade information about the prison murder. In exchange, he wants the GBI to investigate his claim that he was framed on child pornography charges by a corrupt Grant County police department led by Jeffrey and Detective Lena Adams. Nesbitt presents newspaper clippings about women found dead across Georgia since his conviction and insists the real killer is still active. GBI Deputy Director Amanda Wagner orders Will and Faith to interview Lena in Macon and forbids anyone from telling Sara, but Will calls Sara from the prison and tells her everything.
Amanda drives Sara to a funeral home in White County to examine the body of Alexandra McAllister, a 29-year-old hiker whose death was ruled accidental. Sara discovers that nerves in the armpits have been cleanly sliced by a blade rather than torn by animals, and she finds a puncture wound at the fifth cervical vertebra (C5) concealed beneath a superficial scrape. She concludes the killer used a sharp tool to rupture McAllister's spinal cord and severed the arm nerves so the victim could not fight back during a rape, matching the injury found in Beckey Caterino eight years earlier.
The Grant County timeline follows Jeffrey's investigation. After Sara hears a faint clicking sound from Beckey's mouth and realizes the girl is still breathing, she performs emergency surgery in the woods using Jeffrey's Swiss army knife and a pen barrel to bypass a blocked airway. The roughly 30 minutes Beckey lay unattended while officers assumed she was dead may have caused irreversible brain damage. Sara reveals that another student, Thomasina "Tommi" Humphrey, was brutally raped five months earlier. Tommi describes being abducted, drugged with a blue sports drink, and raped while her attacker held a sharp instrument to her neck and ordered her to pretend she was paralyzed. When Leslie Truong, the student who found Beckey, is found dead in the woods with a hammer handle broken off inside her, Jeffrey traces the evidence to Daryl Nesbitt through the hammer's manufacturing mark and Nesbitt's access to his imprisoned stepfather's tools. Jeffrey raids Nesbitt's house, where officers find child pornography on a laptop and a shed containing a cot, a chain bolted to the floor, and stolen hair accessories. Both Jeffrey and Lena sign false sworn statements fabricating the probable cause that underpins Nesbitt's conviction.
In the present, Will and Faith interview Lena, now on maternity leave, who is hostile and accuses Sara of orchestrating the investigation. They then visit Gerald Caterino, Beckey's father, at his home in Milledgeville, where Beckey, now 27, uses a wheelchair and requires constant care. Gerald leads them into a walk-in closet he has transformed into an incident room, its walls covered with articles, police reports, and photographs connected by colored string. He reveals that each victim was missing a hair-related personal item before her disappearance and reported feeling watched. Faith deduces that Beckey gave birth to a son, Heath, roughly nine months after her attack. Gerald confirms he tested Nesbitt's DNA against Heath's, and Nesbitt was excluded as the father, proving someone else attacked Beckey.
Sara briefs the full GBI team, presenting forensic links connecting the victims: a hammer blow to the head, drugging with a blue sports drink likely laced with Rohypnol, a spinal cord puncture at C5 to induce paralysis, and sexual mutilation. Faith identifies a timing pattern: The attacks occur in the last week of March or the last week of October. A civilian investigator's spreadsheet identifies 19 total victims, including three survivors. One survivor, Callie Zanger, a wealthy tax attorney, tells Faith she is certain her abusive ex-husband was responsible and used the attack as leverage in her divorce. Faith is devastated because evidence proves Rod Zanger could not have been the attacker, meaning Callie's sense of victory is built on a lie.
Interspersed with the investigation, Gina Vogel, a 43-year-old Atlanta woman, notices her favorite scrunchie is missing and grows increasingly convinced someone has been inside her house. Her paranoia escalates until she is abducted in a parking lot by a man swinging a hammer. She wakes in the woods, paralyzed and drugged.
Throughout the case, Will and Sara's relationship fractures and slowly mends. Sara spends a night reading Jeffrey's case files and is overwhelmed by grief. When Will finds Jeffrey's boxes in the apartment, the tension explodes. Sara tries to initiate rough sex to avoid talking; Will stops her and walks out. The next morning, Sara goes to his office and tells him she chooses him. Will confesses that her behavior reminded him of his ex-wife Angie, who used physical aggression as the only form of intimacy. They begin to reconnect tentatively.
The case breaks open during the exhumation of victim Shay Van Dorne, whose well-preserved body reveals the same injuries. Sara discovers a piece of latex from a condom lodged between Shay's teeth, introduced after death during the embalming process. Tommi Humphrey then calls Sara and reveals her attacker cried on his knees and said his mother was in the hospital. Sara recalls that Dan Brock, the Grant County coroner and her lifelong friend, had a mother who was hospitalized the same week Tommi was attacked, and that every county where a victim was found falls within Brock's embalming service territory.
Sara agrees to wear a wire into Brock's office. Brock confesses that his crimes began with necrophilia during mortuary school and escalated to attacking living women because he wanted someone who could not reject him. He admits to framing Nesbitt by deliberately leaving the marked hammer inside Truong's body and killing Truong because she had seen him near the Caterino scene. He reveals he has abducted Gina Vogel and will only disclose her location if Sara promises to care for his mother. After giving directions, Brock injects himself with a lethal substance and dies before Will can breach the door. Gina is found alive in the woods near Ellijay, drugged and assaulted but rescued in time.
In the aftermath, Brock's binders reveal nearly 100 documented cases. Nesbitt's health deteriorates in prison. Gerald refuses to test Heath's DNA against Brock's to confirm paternity but enrolls Heath in school for the first time. Lena faces no consequences. Sara sends Tommi Brock's booking photo; Tommi confirms he was her attacker but then cuts off contact. Sara struggles with guilt over not stopping Brock's suicide but gradually moves forward. In the final scene, Sara presents Will with a wedding band inside a McDonald's box. Will pulls from his pocket a small ring with a green stone that belonged to his mother, the color matching Sara's eyes, that he has been carrying for months. Sara says yes.