Seven-year-old Sam Southall loses a tooth and that night he's visited by a sinister, rank, foul-mouthed, mercurial Tooth Fairy, a demonic being that apparently only he can see, but whose malignant influence spills over onto his family and friends. The Tooth Fairy accompanies Sam throughout his growing years, teaching him to make mischief at school, influencing his actions. One day she insists that Sam have his friend Terry sleep over. That same night, Terry's father shoots his wife, his other children and himself.