Ghost Children — Michael B. Dodd

When five-year-old Madison Hawthorne moves into her new home in Salem, Massachusets, she is pleasantly surprised to find four children her own age already living there. In fact, they've been living there for over 200 years. Madison's mother, of course, dismisses her daughter's "imaginary" friends until she can no longer ignore their existence. Though Madison considers the children to be friends, they hold a dark secret that could put the naive child and her parents in mortal danger. There is something else in the house with them, causing even the long-time residents of the home to be terrified of its presence. With the help of two mysterious visitors, the Hawthornes must battle this malevolent being to save the life of their precious child.