Was there just one main character or were there a few about wait till Helen comes?

In "Wait Till Helen Comes" by Mary Downing Hahn, there are multiple main characters, primarily focusing on Molly, her brother Michael, and their stepsister Helen. The story revolves around their interactions and experiences as they navigate family dynamics and the haunting presence of Helen, a ghost. Each character plays a significant role in the unfolding narrative, contributing to the themes of fear, family, and the supernatural.