Ten-year-old Leo's future and the fate of the extraordinary Whippet Hotel, where his father is the maintenance man, are at stake when a series of cryptic boxes leads Leo to hidden floors, strange puzzles, and unexpected alliances.

When she finds the key to a secret passageway leading out of the walled city of Bridewell, twelve-year-old Alexa realizes her lifelong wish to explore the mysterious forests and mountains that lie beyond the wall.

When thirteen-year-old Alexa embarks on a mysterious quest, she finds her old friends Yipes the little man, Murphy the squirrel, Odessa the wolf, and Squire the hawk have been designated to help her.

Although forbidden to see each other, Ryan and Sarah continue their investigation of the mysterious happenings at the dredge by communicating through video clips, text messages, midnight meetings, and journaling. The reader may view videos on a website by using links and passwords found in the text.