Twelve-year old Rainy, an avid hiker, notices small rockslides and gully-washouts occurring on Thunder Mountain and immediately informs the local authorities. When they dismiss her concerns as just 'child's play," Rainy is helpless to do anything but watch, wait and hope she is wrong. If she is right, a major slide is about to happen and her home and the homes of some of her friends are directly in its path! When early winter storms hit the area, followed by unseasonably warm weather, a massive rockslide on Thunder Mountain begins its descent, sweeping everything in its path into the turbulent water of the flood-swollen Neversink River. After a mudslide pushes her house off its foundation and sends it to the edge of a bluff above a raging river, Rainy, her friends and her grandmother, climb to the roof to await help. Cut off from rescuers by downed power lines and flooded roads, Rainy finds she must cope with more than just the rising water, when her grandmother, Suki, takes ill. Can Rainy keep her grandmother alive long enough for help to arrive? She hopes so.For the bluff is beginning to crumble and the house perched precariously on its edge is slowly sinking into the churning water below.