Libby Mannering was 14 and the three other Mannering children weren't babies, so the sitter left them on their own when their parents were out, not realizing that Libby would invite her friend Kit to stay over, and not aware that Kit had the endearing habit of calling random phone numbers and murmuring, ""I know who you really are and what you did."" One such all jarred a maniac loose from his moorings... The carefully controlled plot shifts from the madness of murder to the wild laughter of unsuspecting children and provides some chilling moments.