When Mr. and Mrs. Thompson's regular babysitter can't handle their three children for their anniversary dinner, they turn to a young woman named Emelie. For the kids, initially, that can't be more perfect as Emelie is sweet, lovely, and let them do whatever they want. But as Anna's behaviours gradually turn into something dark and dangerous, big brother Jacob feels clearly that they are not safe anymore. Now he must protect his siblings from the increasingly vicious ploys of the seriously mentally disturbed woman.