David and Pennys strange new home is surrounded by forest. It is the childhood home of their mother, who has recently died. But other creatures live here: magical creatures, like tiny, hairy Pog. He is one of the First Folk, protecting the boundary between the worlds. As the children explore, they discover monsters slipping through from the place Pog calls downways. Meanwhile, David is drawn into the woods by something darker, which insists there is a way he can bring his mother back.
