Since its publication in 1986, the deliciously frightening novel ''Wait Till Helen Comes: A Ghost Story'' has not only haunted countless readers, but has also won eleven state book awards. The spine-chilling tale begins when twelve-year-old Molly and her ten-year-old brother, Michael, learn that they'll be moving to a refurbished old church in rural Maryland with their mother's new husband, Dave, and their younger stepsister, Heather. Heather is an insufferable brat, but that turns out to be the least of the family's worries. When she strikes up a friendship with Helen, the malevolent ghost of a seven-year-old girl who died in a mysterious fire more than a hundred years ago, things really heat up . . . and Heather's unsettling threat, ''Wait till Helen comes,'' becomes a grim reality.