Maggie is an elderly retired CIA agent living quietly in Purity, Maine, where she leads a group of former intelligence operatives known as the Martini Club. Widowed and emotionally guarded, she channels her specialized observation skills into local matters. When her neighbor becomes a suspect in a teenage girl's disappearance, Maggie leverages her past training to uncover the truth without drawing attention to herself.

Jo is the dedicated acting police chief of Purity, Maine. As a local resident deeply familiar with the town's geography and class dynamics, she works hard to prove herself in a role typically dominated by older men. She is focused, no-nonsense, and determined to locate Zoe Conover while managing the influx of dismissive state authorities.

Susan is a middle-class school nurse who has been married to Ethan Conover for two years. She feels anxious and out of place among her husband's wealthy, status-conscious relatives. When her daughter goes missing, Susan's maternal instincts drive her to search frantically, putting her at odds with the seemingly unbothered Conover family.

Reuben is a working-class Purity local who has spent his life caring for his ailing family members. Gruff and weathered, he harbors a deep resentment toward the wealthy summer tourists, particularly the Conovers. His family history is shadowed by his father's violent breakdown decades earlier, leaving Reuben isolated within the community.

Zoe is Susan's 15-year-old daughter and Ethan's stepdaughter. She is a strong, confident swimmer who trains in free diving. Her sudden disappearance after spending an afternoon with a neighbor girl sets off the central investigation of the novel.

Ethan is a writing instructor at Boston College and a struggling novelist working on his second book. Firmly middle-class, he feels insecure and alienated around his wealthier mother and brother. He attempts to balance his stalled writing career with his family obligations.

Elizabeth is the wealthy and traditional matriarch of the Conover family. She prioritizes family loyalty and protecting the Conover name above all else. Her snobbish demeanor makes her daughter-in-law Susan feel unwelcome, and she prefers to keep family matters private from authorities.

Colin is Ethan's older, highly successful brother who works on Wall Street. He drives a luxury car and represents the elite status that eludes his younger brother. He projects confidence and glides smoothly through life alongside his stylish wife.

Brooke is Colin's wife, characterized as half of a "golden couple" who appears perfectly put-together and stylish. She acts as a comforting presence to Susan during the initial stages of Zoe's disappearance, though she remains highly invested in her own son.

Kit is Colin and Brooke's quiet 19-year-old son. He suffered from numerous mysterious health issues as a child, leading to a deeply dependent relationship with his overprotective mother.

Luther is a gruff farmer, former MIT professor, and Maggie Bird's neighbor. His unkempt appearance leads authorities to view him with suspicion after he becomes the last known person to see Zoe Conover before she vanishes. He is fiercely protective of his granddaughter.

Callie is Luther's 14-year-old granddaughter who lives on the farm with him. She spends the afternoon with Zoe shortly before Zoe goes missing, making her one of the last people to interact with her friend.

Declan is a retired CIA agent and a core member of the Martini Club. He is Maggie Bird's closest friend of forty years, and the two share an easy, flirtatious dynamic as they assist in local investigations.

Ben is a tough, physically intimidating retired intelligence operative in the Martini Club. He specializes in video surveillance and utilizes his technical expertise to monitor locations relevant to the mystery.

Ingrid is a retired CIA operative who utilizes her formidable research and computer skills for the Martini Club's unofficial investigations. She tracks down obscure public records and digital footprints.

Lloyd is a retired agent married to Ingrid. He serves as the Martini Club's passionate cook, always prepared with emergency sandwiches to keep the team fueled during their sleuthing.

Arthur is a wealthy, octogenarian bachelor who summers near the Conovers. A retired "energy consultant," he maintains a sharp, watchful presence and acts as a guardian of the elite community's long-held social boundaries.

Hannah is a middle-aged neighbor on Maiden Pond who used to babysit Ethan and Colin Conover. She is a long-standing member of the vacationing community with ties to the town's earlier generations.

Sam is Reuben's late father, a local carpenter who experienced a fatal, violent psychotic episode in 1972. His tragic actions cast a long shadow over his family's reputation in Purity.

Abigail is Reuben's sister. She relies on a wheelchair due to a spinal tumor and depends on her brother for daily care. She advocates for keeping their heads down to survive on their limited means.

Detective Alfond is an arrogant state police investigator assigned to the missing person case. He is dismissive of Jo Thibodeau's authority and relies on aggressive interview tactics.

George is the recently deceased patriarch of the Conover family. His surviving relatives gather at Moonview cottage to hold a memorial service for him.

Anna is Kit Conover's former nanny who left her position under mysterious circumstances. She was one of the few wealthy household employees to show genuine kindness to the local residents.

Finn is Jo's brother. He works as a diver for the Maine Warden Service and assists in searching local bodies of water when evidence suggests a crime.

Farley is a local thief with a criminal record who lives in a dilapidated trailer. He becomes entangled in the investigation due to his proximity to Maiden Pond.

Jesse is Callie's father, recently released from prison. His presence causes deep anxiety for Luther Yount, who fears Jesse's influence will harm Callie.

Vivian is a woman who vanished from a rented cottage on Maiden Pond in 1972. The unsolved nature of her disappearance piques the interest of researchers decades later.

Catherine is Vivian Stillwater's sister, now an elderly woman living in a retirement community. She holds fragmented answers about her sister's sudden disappearance.

Dr. Greene is Hannah's late father, an early owner of a cottage on Maiden Pond whose professional connections intertwine with the town's history.