Lester is a 28-year-old divorced father seeking therapy to discuss the tragic deaths of his three children. Harboring deep-seated paranoias and expressing rigid views on masculinity, he insists on harsh parenting methods, such as refusing to comfort his son with a bottle, to prevent his children from becoming soft. He presents a deeply disturbed psychological state, carrying immense guilt while simultaneously projecting blame onto a supernatural entity. During his session, he speaks freely about his resentments, offering derogatory opinions on the women's liberation movement and making cruel comparisons to casualties of the Vietnam War.

Dr. Harper is a psychiatrist tasked with evaluating and treating a deeply disturbed father in a closed-door office session. He maintains a quiet, observant demeanor, allowing his patient to speak at length about his fractured marriage and family tragedies. He monitors physical cues closely to better understand his client's state of mind, specifically noting Lester's frightening, rubbery smiles and defensive posture. When appropriate, he interjects to offer logical medical explanations for seemingly impossible events, such as suggesting a child's babbling was simply an attempt to say the word closet.

The Boogeyman is a monstrous, shadowy entity that allegedly lives in the closets of family homes. Characterized by an awful smell resembling a dead mouse, a scarecrow-like head, and long claws, the creature feeds on fear and targets vulnerable children in the dark. It operates as the physical manifestation of terror, always heralded by a closet door left open just a crack. According to accounts, the creature slithers in the shadows, breaks household mirrors, and leaves muddy tracks across the floor when it grows bolder.

Rita is the mother of three children whose marriage deteriorates under the weight of successive family tragedies and domestic friction. She attempts to offer maternal comfort to her fearful children but frequently faces hostility and strict disciplinary rules from her husband, who threatens her with violence. She relies on an IUD for birth control, the failure of which causes further resentment in her household. She eventually seeks physical distance from her toxic domestic environment when an accident requires her to care for her own mother in another town.

Denny is the firstborn son of the Billings family. He develops a severe fear of the dark and the creature he believes lives in his bedroom closet, prompting him to cry out for comfort at night. His natural childhood anxieties clash violently with the demand for toughness enforced in his household. After his sudden death, his physical state is cruelly compared to a war casualty by his own father, while doctors officially rule his passing as crib death.

Shirl is the second child of the Billings family. Following her brother's passing, she is moved out of the master bedroom and forced to sleep alone in the same room where her sibling suffered. As she grows slightly older, she begins experiencing the same nighttime terrors, screaming about something slithering in the shadows of her room. She attempts to warn her parents about the monster, repeating a word that sounds like claws, before suffering a fatal convulsion in the dark.

Andy is the youngest child of the Billings family, born despite his mother's use of a contraceptive device. For the first year of his life following a move to Waterbury, he experiences a relatively peaceful home environment. However, as the household atmosphere darkens again and unexplained events begin occurring in the new house, he is relocated back to an isolated nursery. He becomes entirely vulnerable to the shadows when his parents stop sharing a room with him.