When Eric Johnson moved from Philadelphia a year ago, he didn't have any friends in the Lehigh Valley. Now he had a lot of them, just not the usual sort for a twelve-year old boy. Aside from Tommy Kuhns and Stephanie Fuller-two young children his own age-Eric's house was often visited by Norse Gods, Rock Dwarves, Valkyr, and unfortunately the occasional Frost Giant. And most teens weren't caught up in a war that crossed multiple dimensions.Now the Frost Giants were trying to get access to Enigma Caverns and the Lost River, so they could continue their battle against the Aesir. Eric, Tommy and Stephanie had to find out why the Giants really wanted the Lost River and stop the Giants from taking control of Enigma Caverns. Then Eric is thrown into the Lost River and disappears, and things really get strange! The Giants are looking for a way back to their home dimension and they believe Eric knows the way home, or at least how to find the way home. So they kidnap Eric's aunt and demand an exchange: the knowledge for his aunt. But Eric has two secret weapons on his side: the ancient battle computer known as MMR and a creation of the Giants' own laboratories-a giant dragon called Fornir.