Something wicked has awoken under the streets of Dublin... When his dad is offered a job working on the new Metro tunnel; Arthur has to move to Dublin with him. While exploring a hidden underground river, Arthur and his new friends Will and Ash find a mysterious glowing pendant. The pendant depicts a giant snake strangling the trunk of a tree. The friends soon figure out that the pendant is a warning, a sign that something evil is waiting underneath the city. Something that's been imprisoned for a thousand years, something left by the Vikings, something that can - and will - destroy the city, and then the world. ""Lively and adventurous. . . The excitement is full blast from beginning to end. . . Adventure lovers will hand on to every word and eagerly await the next book in the series.""-VOYA