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.
At a refugee camp following the eruption of Mt. Vesuvius which buried Pompeii, Flavia and her friends discover that children are disappearing and a very powerful citizen might be involved.