Molly, the 12-year-old narrator, and her brother Michael dislike their bratty 5-year-old stepsister Heather and resent the family move to an isolated converted church in the country. The adjourning graveyard frightens Molly, but Heather seems drawn to it. Molly discovers that the ghost of a child (Helen) who died in a fire a century ago wants to lure Heather to her doom. Molly determines to save her stepsister. In so doing, she learns that Heather's strange behavior stems from her feelings of guilt at having accidentally caused her mother's death by playing near a stove and starting a fire. Eventually, Molly wrests Heather from Helen's arms as the ghost attempts to drown them. The girls discover the skeletons of Helen's parents, and their burial finally puts to rest Helen's spirit.