Hal is a father of two and former resident of Connecticut who currently struggles with unemployment. He harbors deep, unresolved trauma from a childhood marked by sudden abandonments and tragic accidents. As an adult, he is increasingly quick-tempered and prone to violent outbursts that surprise even himself. His discovery of an old wind-up monkey toy in the attic triggers severe anxiety and forces him to confront terrifying memories from his past.

The monkey is a vintage wind-up toy covered in matted brown fur. It features glassy amber eyes and a permanent, eerie grin. Originally found among the abandoned possessions of Hal's father, the toy holds a sinister, seemingly supernatural influence. It operates unpredictably and often clashes its cymbals without being wound. The object exerts a strange magnetic pull on children while eliciting deep dread in those who understand its nature.

Petey is Hal and Terry's sweet-tempered younger son. He possesses a natural curiosity and innocence that sharply contrasts with the growing tension in his household. When he encounters the strange monkey toy, he feels an overwhelming compulsion to wind its key, even as the object frightens him. His vulnerability makes him the primary focal point of his father's protective instincts.

Terry is Hal's wife, currently dealing with a marriage marked by emotional distance and poor communication. She copes with the stress of her husband's two-year unemployment and unpredictable temper by withdrawing and taking Valium. She remains largely dismissive of Hal's intense reaction to the monkey toy, viewing his fears as irrational behavior brought on by general strain.

Dennis is Hal and Terry's twelve-year-old son. He is currently in a rebellious phase and frequently challenges his father's authority. His sarcastic questioning of his father's mental stability triggers a surprisingly physical and violent response from Hal. Dennis struggles with the tense, volatile atmosphere of his home life.

Bill is Hal's older brother, a boy who shared the trauma of their father's early abandonment. He helps Hal explore a closet full of their missing father's belongings, searching for a connection to the man they never knew. Bill brings the strange monkey toy into their shared bedroom, setting the stage for the family's early supernatural encounters.

Aunt Ida is Hal's adoptive mother figure who took him in after his parents died. She lived in Casco, Maine, with her husband Will. Her recent death from a stroke brings Hal and his family back to her home, where they must clear out her attic and confront the forgotten relics of Hal's past.

Uncle Will is Aunt Ida's husband. He steps in to help raise Hal and Bill after the boys lose their mother. He owns a rowboat and a boathouse by the lake, which eventually becomes the setting for Hal's desperate attempt to dispose of the cursed toy.

Hal and Bill's mother is a single parent doing her best to raise two boys after her husband abandons the family. She works hard to provide for them but is frequently absent due to her responsibilities, leaving the boys in the care of babysitters.

Hal's father is a merchant mariner who abandons his family when his sons are very young. He leaves behind a closet crammed full of nautical belongings and mysterious items. His disappearance creates a profound psychological wound in his children, who search through his abandoned possessions looking for a connection.

Beulah is one of the babysitters tasked with watching Hal and Bill while their mother works. She is present during the early days when Hal first experiences the terrifying nighttime activity of the monkey toy.

Johnny is a childhood friend of Hal. They spend time together during Hal's youth, climbing trees and playing before an accident prompts Hal to take drastic measures regarding his old wind-up toy.