Luke and Lisa are protesting with a group of friends at a construction site. They don't want a new road cutting through old Mott Hill. They believe that it holds a terrible secret, a large predator roaming the area. Suddenly, the diggers disappear into the ground! Have the workers stumbled on an opening to another world? Something evil lies on the other side of this underground door to darkness. The exploits of the characters are interesting, and the book seems to deal with protest movements and environmental issues, too. The chapter topics are an added draw, truly capturing the mysterious aura of the book. The cover in brown, yellow and other dark shades does the same. As usual with Stone Arch books there are "About the Author" and "About the Illustrator" sections, a glossary, and Internet sites. This book is particularly good for students who need a structured vocabulary so that they have some choices in reading material. It is wonderful for the classroom teacher because of the discussion questions and writing prompts.