Three ""ex--human beings""--Lady Cordelia, Sir James, and Bobble (a chimney-sweep girl)--find their ""Unwakeful Serenity"" shattered by the three young Sweets (""interesting children but not particularly nice""), whose newly rich parents have rented the house where the ghosts had quietly resided with old Mercia Porterhouse. After the kids inadvertently dump frog spawn on James (in the bottle where he lives), Cordelia attempts a diplomatic meeting. Her pleas for understanding are met with curiosity but disrespect; the ghosts are forced to call in a really frightening reinforcement in the form of a Stone Age Scottish ghost before the children become their unexpected allies. Besides the refreshingly ornery kids and their oblivious, backgammon-hooked parents, there's a lot of humor in the new ""facts"" introduced about ghosts: they inhabit things rather than places, float upside-down when perturbed, and must concentrate to pass through walls, This one would be fun to share aloud. Frequent full-page black-and-white illustrations add to the humor.