The novel alternates between past and present timelines, weaving together a romantic thriller about trauma, identity, and the search for a stolen child.
In the "Before" timeline, nineteen-year-old Josie Stratton, a University of Cincinnati (UC) student, goes to a club with her best friend Reagan and their charming friend Cooper, who appears to be gay. Josie leaves early and walks home to the Clifton apartment she shares with Reagan. That night, a man in a black ski mask strangles and drugs her. She wakes chained to a concrete wall in a warehouse. Her masked captor calls her by name, stutters, and brands her a "whore." She recognizes his scent and identifies him as her downstairs neighbor, Marshall Landish.
Eight years later, Detective Zach Copeland responds to a scene where a young woman's body has been found chained in the basement of an abandoned Clifton house. The shackles remind Zach of Josie Stratton's case from his first week as a rookie, when he guarded her hospital room after she escaped nearly a year of captivity. Zach and his partner, Detective Jimmy Keene, review the old file: Josie was repeatedly raped, starved, and had the Latin phrase "casus belli" carved into her thigh, meaning both "where the blame lies" and "an act that justifies war." She became pregnant and gave birth while shackled, but her captor took the baby before she escaped. Landish was found dead of an apparent suicide, and the case was closed. The baby was never found.
The new victim, Aria Glazer, died of starvation and was sexually assaulted, with the same phrase carved into her thigh. The killer's use of a condom distinguishes the crime from the original case.
In Oxford, Ohio, Josie lives alone in a farmhouse inherited from her late Aunt Mavis, restoring it as a bed-and-breakfast. Her cousin Archie Phillips pressures her to sell and threatens a lawsuit. In her locked bedroom, bulletin boards display eight years of research into her missing son.
Zach informs Josie about the copycat case. That night, someone leaves a dead rat stabbed with a knife on her kitchen table, echoing her captivity. A second victim, Miriam Bellanger, a UC student and city council member's daughter, is discovered with the identical method. The department forms a task force.
Miriam's diary references sex on "PM's desk" on Wednesday nights. Zach identifies "PM" as Professor Vaughn Merrick, who teaches Miriam's Wednesday night class. He learns Josie and Aria also had relationships with Merrick, establishing a link among all three women.
Josie's mother, Diana Stratton, is found murdered, strangled, with cigarette burns mirroring what Diana inflicted on Josie as a child. The same phrase is carved into her thigh. Josie tells Zach that only her captor ever saw her childhood burn scars, deepening the mystery. Merrick admits to affairs with Aria and Miriam but denies involvement in their deaths.
A terrifying phone call follows: Someone impersonating Landish's voice and stutter claims responsibility for the rat and Diana's murder. Zach's sergeant sends Josie to a safe house in Tennessee, where she finally confronts her captivity memories. Jimmy raises troubling questions about the original case: No DNA or fingerprints belonging to Landish were found in the warehouse, no ski mask was recovered from his apartment, and unidentified hairs on the mattress had been dismissed. He suggests the real captor impersonated Landish and staged his suicide. Josie resists the theory but recalls her captor's stutter sometimes disappearing under stress. Zach discovers Landish was color blind, yet Josie remembers her captor identifying her red underwear by color.
Josie and Zach's relationship deepens into physical intimacy, and Josie discovers she is not irreparably broken. They visit Landish's sister, Linda Winston, who insists her brother was innocent. Linda clarifies that Marshall's stutter worsened under stress rather than disappearing, and confirms color blindness ran in the family. Viewing a photograph of Marshall, Josie tells Zach with certainty: Those were not Marshall's eyes behind that mask.
Interspersed "Before" chapters chronicle Josie's pregnancy and escape. Her captor stops the sexual assaults after feeling the baby move. Josie labors alone, delivering a boy she names Caleb. When infection sets in, she begs her captor to take the baby to safety. He seizes Caleb and returns to say the child is "taken care of." In his final food delivery, Josie finds a toy with a tiny metal spring. She uses it to pick the lock of her shackle and escapes through a basement window into the freezing night. In the hospital, her eyes lock with those of a young officer: Zach Copeland.
In the present, Josie reunites with Reagan and Cooper to discuss Merrick. Reagan confesses she once slept with Merrick. Immediately after Cooper leaves, the threatening call arrives, its timing suspicious. When Reagan disappears despite police surveillance, the investigation accelerates. A former neighbor of the Merricks mentions they once fostered a boy named Charlie. Viewing a childhood photo, Josie recognizes him: Charlie is Cooper. No records exist for Cooper Hart. His real name is Charles Hartsman.
Merrick's ex-wife Alicia reveals Charlie was a gifted impersonator the family called "our little copycat." After his behavior worsened, the Merricks returned him to the foster system. Social worker Janelle Gilbert reveals Charlie was then placed with a couple who chained him in their basement, starved him, and left him alone for days. Janelle confesses that years later, Charlie brought her a newborn, claiming his girlfriend had died. Believing she owed Charlie, Janelle arranged a private adoption with the Davies family in Kentucky. Josie's son, now a healthy eight-year-old named Reed, has been living 15 minutes away.
Charles lures Josie to a baseball field where Reed plays by impersonating her lawyer's voice. Josie sneaks away from her protection detail with help from Rain, a neighbor she befriended. Charlie approaches from behind, cycles through impersonated voices, tells Josie the "final battle is over," and hands her the toy she used to escape, saying he was rooting for her. He vanishes. Rain is found unconscious but unharmed.
Zach decodes Charlie's parting clue and locates Reagan alive. Realizing Charlie's true target was Merrick, Zach finds the professor chained in his own basement, mutilated but alive, with the Latin words for "the war is over" written in blood on the wall. Charlie steals 2 million dollars from a woman he seduced and disappears completely.
Zach, who is adopted himself, gently raises concerns about uprooting Reed from the only family he has ever known. Josie makes the agonizing decision to relinquish her parental rights so Reed can remain with the Davies family. She signs the papers, asking only for yearly updates and leaving Reed a letter.
After weeks apart, Josie appears at Zach's office. She acknowledges her fear of repeating destructive patterns but says she no longer believes she is broken. Zach tells her he loves her, and they kiss. The epilogue takes place years later: Josie and Zach have married and filled the farmhouse with their own family. Pregnant with their daughter Arryn, named for Zach's late brother Aaron, Josie goes into labor as the sun sets. The novel closes with her gazing at the wide-open sky she once dreamed of seeing again from her prison cell.