The Tower of Shadows (The Elsewhere Chronicles)

The time has come to confront the Master of Shadows. Rebecca, Max, and Theo must follow Grandpa Gabe into the heart of the Master's realm, the Tower of Shadows. But can Grandpa Gabe be trusted? There's a reason he's so familiar with the dark powers that rule Elsewhere: he created them. Grandpa Gabe's plan might just be a suicide mission, but it's their last chance to save our world—and Rebecca's life.