Isabelle is a former magazine writer who lives in Savannah, Georgia. She suffers from severe insomnia, having not slept properly in the year since her infant son, Mason, disappeared from his crib. Her desperation to find him alienates her from those around her and leads her to reluctantly engage with the true crime community. She frequently experiences unsettling memories of her childhood sleepwalking and the tragic losses of her two younger sisters.

Benjamin is Isabelle's estranged husband and her former boss at The Grit magazine. Following Mason's disappearance, he moves out of their shared home and urges Isabelle to accept the likelihood of their son's death. Charismatic and handsome, he quickly begins dating someone new, creating significant emotional friction whenever he and Isabelle interact.

Waylon is a self-funded true crime podcaster who takes an immediate interest in Mason's case. He claims his dedication to true crime stems from the unsolved murder of his sister. By offering Isabelle a platform and helping her review old evidence, he slowly breaks through her hostility toward the true crime community.

Valerie is a young, attractive woman who works as a grief counselor in Savannah. She begins dating Benjamin Drake following his separation from Isabelle. Her physical appearance is striking to Isabelle, as she strongly resembles both Isabelle and Benjamin's deceased first wife, Allison.

Allison is Benjamin's first wife, a woman who struggled with addiction and possessed professional aspirations in law before her tragic death. Her passing occurred shortly after Benjamin and Isabelle first met, and the circumstances surrounding her suspected overdose remain a sensitive topic.

Mason is the infant son of Isabelle and Benjamin. He vanished from his crib in the middle of the night a year before the main events of the story. Described as a fussy and difficult baby, his absence leaves a profound void that entirely consumes his mother's life.

Margaret is Isabelle's younger sister who died in a childhood accident. During their youth at the historic Hayworth Mansion, she frequently expressed anxiety over Isabelle's nighttime wanderings and the general eerie atmosphere of their home.

Eloise is the youngest daughter of the Rhett family, who was lost as an infant. Her death left a permanent mark on the family, initiating a cycle of trauma and emotional suppression that deeply affected her surviving sisters.

Isabelle's mother is a former painter who lives in Beaufort, South Carolina. Following the tragic losses of her younger daughters, she withdrew emotionally and abandoned her art. She currently maintains a distant, strained relationship with Isabelle, avoiding discussions about the past.

Isabelle's father is a retired congressman who prioritized his political legacy and public image above his family's mental health. By insisting on keeping up appearances, he established a culture of secrecy within the Rhett household that prevented true healing.

Detective Dozier is the local law enforcement officer assigned to Mason's case. He finds himself caught between formal police protocol and Isabelle's desperate, often intrusive demands for action. He repeatedly warns her against acting impulsively or harassing her neighbors.

Kasey is a staff member at The Grit magazine and served as Isabelle's mentor during her brief time working there. She remains one of the few people from Isabelle's past who actively reaches out to check on her well-being.

Dr. Harris is a sleep specialist who treats Isabelle for her severe insomnia. He provides medical insight into the dangers of sleep deprivation, including the potential for hallucinations and extreme paranoia.

Paul is a redheaded man living in Isabelle's neighborhood who possesses previous drug offenses on his record. He is highly defensive of his privacy and threatens to call the police when Isabelle interrogates him about his activities.

An elderly individual who spends time observing the neighborhood from his son's porch. He unnerves Isabelle by claiming he has watched her walk outside late at night, feeding into her fears about her sleepwalking habits.

Abigail is a woman with an intense interest in true crime who previously attended the cathedral's grief counseling sessions due to her struggles with infertility. Her presence at the convention catches Isabelle's attention.