Ethan is a forty-year-old man dealing with severe insomnia following the disappearance of his childhood best friend thirty years ago. He recently moved back into his parents' vacant house in the affluent neighborhood of Hemlock Circle. The unresolved mystery drives him to investigate what truly happened in 1994, as he struggles to differentiate between reality and his own fractured memories.

Billy is a ten-year-old boy with a deep fascination for ghosts and the supernatural. He feels isolated from his peers but shares a close, trusting bond with his neighbor Ethan. His sudden disappearance from a backyard tent leaves a permanent scar on the Hemlock Circle community and becomes the central mystery of the narrative.

Ashley is Ethan's former childhood babysitter who recently moved back to Hemlock Circle to care for her aging father. In 1994, she was a teenager with ambitions to leave suburbia and pursue a music career. She now lives a quiet life as a devoted mother, checking in on Ethan as he deals with his renewed obsession with the past.

Henry is Ashley's ten-year-old son, a quiet boy with a surprisingly formal manner of speaking. His serious demeanor, love for reading scary stories, and questions about monsters remind Ethan strongly of Billy. He serves as a living link to the past, prompting the adults around him to reflect on their own childhood experiences.

Russ is a childhood friend of Ethan and Billy who still lives in Hemlock Circle. Once an awkward kid eager to fit in, he has grown into a confident, successful adult who owns a sporting goods store. He provides Ethan with a sense of camaraderie, though their reunion emphasizes the drastically different paths their lives have taken.

Andy is Billy's younger brother, who was only seven years old at the time of the disappearance. He spent his early childhood feeling left out of Billy's adventures with his neighborhood friends. The sudden loss of his brother severely impacts his development and perspective on the world.

Claudia is Ethan's wife, from whom he is currently separated. They met at a college party, and she provided him with his only real respite from his childhood trauma. Their relationship ultimately fractured due to Ethan's reluctance to start a family.

Joyce is Ethan's mother, a traditional homemaker who briefly found satisfaction working outside the home. Her sudden job loss in the summer of 1994 creates tension in the Marsh household. She feels isolated within the affluent neighborhood and struggles to find personal fulfillment.

Fred is Ethan's father, a pragmatic man who provides for his family but sometimes lacks emotional intuition. He often dismisses the neighborhood gossip and struggles to understand his wife's complex feelings about her role as a homemaker.

Mary Ellen is Billy and Andy's mother, a woman consumed by undiagnosed anxiety. She perceives the world as a dangerous place and desperately tries to shield her children from physical and emotional harm. Her overwhelming worry often feels stifling to her sons.

Vance is Ashley's aging father, whose deteriorating health prompted her return to Hemlock Circle. Once a pugnacious and sharp man, he now struggles with confusion and cognitive decline. He deeply unsettles Ethan by claiming to have seen the missing Barringer boy in his backyard.

Ragesh is another childhood peer from Hemlock Circle who grew up to become a police detective. As a teenager, he was somewhat cruel and skeptical, but he now approaches his job with professional gravity. He serves as Ethan's primary source of official information regarding the ongoing investigation.

Cassandra is a state police detective with an extensive knowledge of the Barringer case. She explains that Billy's disappearance motivated her to join law enforcement. She operates under the firm theory that Billy was taken by someone familiar and trusted within the community.

Fritz is a long-time resident of Hemlock Circle and the husband of Alice. He works closely with the enigmatic Hawthorne Institute. His somewhat suspicious behavior makes him a person of interest in Ethan's amateur investigation.

Johnny is Russ's older brother who died as a teenager from an overdose prior to the main events of 1994. His tragic death left a dark cloud over the Chen household and deeply affected his younger brother's development.

Ezra is the wealthy, eccentric founder of the Hawthorne Institute, located in the woods near Hemlock Circle. He possesses a deep fascination with the occult and the possibility of communicating with spirits, creating a secretive environment that sparks numerous neighborhood rumors.