There's a Dead Person Following My Sister Around — Vivian Vande Velde

Imaginary friend--or GHOST?
When Ted's five-year-old sister, Vicki, invents an imaginary friend, no one is too concerned ... until her "friend," Marella, starts to move things. Ted is sure that Marella is a ghost. But why would a ghost haunt Vicki? And why is Marella terrified of another ghost -- a dark figure that seems to be haunting Ted? A good ghost is one thing. An evil ghost, determined to use Ted and his sister to get her own way, is another...