Emelie. The Thompsons, a loving family living in a peaceful suburb are the very definition of wholesome normalcy. But on the eve of their thirteenth wedding anniversary their usual babysitter has to cancel, leaving Dan and Joyce to call upon a new girl who seems like a dream come true to their three children: Christopher, Sally and Jacob. As the night creeps on, the kids slowly realize something is very wrong and this woman is not who she claims to be. Jacob, the eldest, must grow up quickly if he wants to save his siblings from the sinister intentions of Emelie, the disturbed woman masquerading as their babysitter.