A mysterious, recurring dream leads Sam London, twelve, to discover that mythical creatures are real and living in our national parks and that his dream may mean that the secret of their existence is in danger.

"Following the heartbreaking conclusion of his second case, Sam has spent his days searching for the swan maiden. Driven by his belief the maiden is still alive, he sets out with Dr. Vance Vantana and Tashi on a forbidden quest to reunite his family. But the journey is long and treacherous and will lead them through the lair of the Mongolian Death Worm--a terrifying creature that has broken the Gryphon's Law and is attacking anyone who dares to cross...