Their magic treehouse takes Annie and Jack to Pompeii just as Vesuvius is about to erupt, and they must find a Roman scroll before everything is covered with burning ash.

Ten-year-old Flavia and her friends encounter the Roman admiral Pliny before making a journey to her uncle's farm near Mt. Vesuvius, where they try to solve a riddle, reunite a family, and get out of the path of a natural disaster.

The beast beneath the mountain is restless... No one in the bustling city of Pompeii worries when the ground trembles beneath their feet. The beast under the mountain Vesuvius, high above the city, wakes up angry sometimes -- and always goes back to sleep. But Marcus is afraid. He knows something is terribly wrong -- and his father, who trusts science more than mythical beasts, agrees. When Vesuvius explodes into a cloud of fiery ash and rocks fall...