When Polly's dad and his new wife Veronica Kreep go on their honeymoon, the Winkler kids are stuck alone with their weird new step-siblings ...in the Kreeps' spooky old mansion! Things get even worse when their sinister sitter, Ms Pearl, shows up. Even sunny Joy and oblivious Petey have to admit that Polly might be right: they have to find a way to get rid of Ms Pearl. And they just might need the Kreep kids' help to do it.