Henry, Angie, and Cecil have unlocked the secret of the Archway Room, and now they are ready to begin their greatest adventure yet. Beyond the Waters lies the Night Side of Atlas World-a realm that mirrors their familiar Day Side in many ways, yet holds surprises that challenge everything they thought they knew. As the three Travelers explore this strange new territory, they discover landscapes that echo the places they've visited before. But the Night Side has its own inhabitants, its own rules, and its own dangers lurking in the perpetual night.
When they find another Archway Room on the Night Side, the friends get a glimpse of even more distant regions of Atlas World. Instead of access, though, they hit a wall-the Atlas in this room is locked. Frustrated and seeking answers, Henry turns to the one person who might understand: his grandfather.
When the three Travelers ask for his help, they uncover the biggest revelation of all. Henry's grandparents have been keeping secrets that will change everything the Travelers thought they knew about The Atlas, about Atlas World, and about their own incredible journey.
Some doors can only be opened when you're ready for what lies beyond.
The final adventure begins. The greatest secrets await. And the possibilities are truly infinite.