She has stayed up by virtue of adrenaline and sheer force of will. Her parents have warned her, but she is heedless. The house is dark and foreboding, but she is fearless.
Flashlight in pudgy hand, she steals from corner to corner, padding on stocking feet through the house and down the stairs. The sofa will provide cover, and it is behind it she settles in to wait in secret.
Will it be Santa coming down the chimney to leave presents and devour the milk and cookies, or some nameless horror, intent on devouring her? She will not be caught unawares.