Molly and Michael just can't get along with their new step-sister Heather. Heather's a brat who's always trying to get them in trouble no matter how nice they are to her. Things get worse when they move to a church in the country, because in their backyard is a graveyard and in the graveyard is a mysterious grave with Heather's initials on it. Soon Heather is being even brattier than usual and warning Michael and Molly that they better "wait 'til Helen comes" because then they'll be sorry. Only Molly believes that Heather is seeing a ghost named Helen and is in danger of being possessed. Is there really a ghost? Can Molly convince her family in time? Will she be able to save Heather? Does she even want to save the brat? Curl up with this spine-tingler to find out!