Sixth-grader Neely Bradford and her little brother, Grub, are fascinated with Halcyon House, the abandoned 19th-century mansion near their Pacific coast home. There are rumors about the Hutchinson family who built the house; people say the place is haunted by the ghost of a girl. Imaginative Neely loves to entertain Grub by embellishing the tales with details of her own. When the children enter the house through an open window, and make a nursery full of wonderful old toys their private playroom, sensitive Grub seems to actually see and speak to the ghost. Then strange, nervous Curtis Hutchinson and his parents move back to the mansion, changing everything. Eerie foreboding weaves through this well-paced tale of two children absorbed with haunting questions about the past. Tension mounts to a convincing, hair-raising climax as the children return to the house again and again, unable to resist its mysterious appeal in spite of the growing sense of danger. Using Neely's imaginative point of view as a bridge, Snyder (Cat Running, 1994, etc.) successfully blends the supernatural with ordinary events, making this a book not only for fantasy fans but for readers who usually prefer realistic fiction. (Fiction. 10-14)