"Albert and his Balance Keepers teammates have been called back to the Core for immediate action! There s a serious Imbalance in the fantastical underground Realm of Belltroll. Without intervention, everything from New York to Yellowstone above could be swallowed by earthquakes. It s clear the mysterious traitor who caused last term s chaos is at it again, and with a vengeance. Albert s super-magical Master Tile helped fix the Ponderay and Calderon Realms in previous terms, but now it seems the Tile may be more trouble than it s worth. Because if it s Albert s Tile the traitor is after, there will have to be a battle sooner or later, and only one of them can win..."--From publisher.

Ages 8-12. Kirkus Reviews.