House of Haunted Secrets

A couple of teenage sleuths who follow a cat into an old boarded up mansion find themselves embroiled in a decades long mystery. Overturned furniture, hand painted portraits hung with faces turned toward the wall, hidden rooms and staircases, full suitcases, and several other mysterious findings seem to show an abrupt departure. But who? And why? What would cause people to leave all of their belongings to never return? What would the walls tell about the history and happenings of this old house?