Jack is a working-class husband and father living in Live Oak, Louisiana, who repairs swamp boats for a living. He carries unresolved trauma and repressed memories from his troubled childhood in rural Georgia. Desiring to protect his family, he routinely relies on secrecy and hides his past experiences from his wife.

Charlie is Jack and Aimee's six-year-old daughter. Outwardly innocent and small for her age, she begins exhibiting unnatural strength and emotional detachment following the car accident. She claims to speak with a hidden presence in her room, using her youthful vulnerability to confuse her family and manipulate domestic situations.

Aimee is Jack's wife. She strongly prefers rational explanations to manage her family's escalating instability. She frequently visits antique shops and worries about household finances. As unexplainable physical events occur in her home, she desperately seeks medical diagnoses for her youngest daughter, isolating herself when those clinical explanations fail.

The Trucker, whom Charlie refers to as "Mr. Scratch," is a giant, bearded man with needlepoint teeth who drives a rusty red pickup. He acts as a physical manifestation or associate of the dark entity connected to Jack's childhood, appearing at significant moments of trauma.

Abby is the ten-year-old daughter of Jack and Aimee. She is perceptive and quick to notice the disturbing changes in her younger sister's behavior. As the tension in the house escalates, she becomes fearful of her sibling and seeks refuge away from their shared bedroom.

Patricia is Aimee's mother, a woman who embodies Southern genteel snobbery. She openly disapproves of Jack's working-class background and questions his ability to provide for her daughter. Her quickness to believe the worst about Jack exacerbates the family's internal divisions.

Reagan is Jack's best friend and bandmate. His mother took Jack in when Jack arrived in Louisiana as a teenage runaway. Unaware of the supernatural forces at play, Reagan views Jack's problems entirely through the lens of ordinary marital and financial stress.

Gilda is Jack's mother, appearing in his fragmented childhood memories. Living in a dilapidated trailer in Rosewood, Georgia, she struggled with severe depression and alcohol addiction. She was the first to notice the disturbing, unnatural changes in her son's behavior.

Stephen is Jack's father, residing in a rural Georgia trailer during Jack's youth. He initially dismisses his wife's concerns about their son's bizarre actions but eventually resorts to boarding up the boy's bedroom door out of desperation.

Nubs is the Winter family's dog. He is highly sensitive to the unnatural changes occurring within the home, demonstrating fear and anxiety as the supernatural disturbances escalate.

Dr. Markin is a psychiatrist Aimee consults to explain Charlie's alarming behavior. He attempts to evaluate the child for post-traumatic stress or schizophrenia but fails to get an accurate family history due to Jack's evasiveness.

Dr. Copeland is the psychologist Gilda Winter paid with her life savings to examine young Jack. He evaluates the boy using inkblot tests but dismisses Jack's descriptions of a shadow creature as mere tricks of passing headlights.

Mabel is the elderly co-owner of an antique shop in Live Oak. She serves as a sympathetic confidant for Aimee during times of marital stress, encouraging her to seek professional psychological help for Charlie.

Arnold is Patricia's husband and Aimee's father. He provides structural support to his daughter's family and is part of the Riley family dynamic that scrutinizes Jack's working-class lifestyle.

Ginny is a local historian in Jack's childhood hometown. She possesses knowledge about the dark legends and tragic events surrounding the old Winter property, sharing the town's grim rumors with visitors.

Phil is the elderly co-owner of Mabel's Curious Curios. He helps run the antique shop where Aimee frequently visits to find solace away from her chaotic household.