The story begins when siblings Tess and Toby discover a tiny tintype portrait of an unknown female ancestor in the family's Memory Box. Intrigued by the antique photograph, they remove it from the box. Over the course of an evening, the bright image of the photograph inexplicably fades away. The children fear that it's forever lost. They set off on an adventure, both real and imagined, seeking clues to her identity. Along the way, they are introduced to genealogy, antiques and early photography. The story ends at the start of a new journey - a journey of self-discovery for the children when they begin their own family tree project.