This month we will read Wait Till Helen Comes by Mary Downing Hahn. From the publisher:
Ghost story master Mary Downing Hahn spins a suspenseful yarn about two children who dislike their malicious younger stepsister, Heather—and tensions that escalate when Heather starts talking to a ghost named Helen.
In a chilling ghost story that is also an insightful family drama, Molly, 12, and her brother Michael, 10, are wary of their sneaky seven-year-old stepsister, Heather. Ever since they became a blended family, Heather has lied, tattled, and created tension between their parents. Worst of all, Heather claims she has been talking to a ghost named Helen, and she warns Molly and Michael that Helen is coming for them. Molly feels certain Heather is getting herself into some kind of danger, but every time she tries to help, Heather maneuvers to get her into trouble. The whole family is at odds. It seems as if things can’t get any worse. But they do—when Helen comes.