The highly-anticipated eighth book in the #1 New York Times, Wall Street Journal, and USA Today bestselling series, with over 10 million copies in print!

Picking up after Quint and Dirk's Hero Quest, the Last Kids are happily reunited—but quickly faced with a monstrous new mission. Inside an other-dimensional fortress, the evil Thrull, alongside a vile new villain, is carrying out a sinister plan. Jack, Quint, June and Dirk must make their own plans to infiltrate the stronghold before Thrull gets any closer to completing the mysterious Tower, a structure that could ultimately spell doom for this dimension.