The Secret of Zoom by Lynne Jonell

Christina lives in an old stone mansion on the edge of a forest surrounded by barbed wire and signs that read TRESPASSERSWILL BE BOILED. Deep within the forest is the laboratory where her father works—and where her mother was blown to bits years ago.
Christina is not supposed to talk to the orphans down the road. But when an orphan boy named Taft tells her of a secret tunnel, she finds it and helps him escape. Soon she and Taft discover there is far more to the orphanage and the mystery of her mother’s supposed death than they ever suspected.

Dog Gone Note: This book is in excellent condition.