The Roman Mysteries: The Secrets of Vesuvius: Book 2 by Caroline Lawrence
It's the summer of AD 79 and Flavia Gemina and her friends, Jonathan, Nubia and Lupus, set sail for the Bay of Naples where they are going to stay with Flavia's uncle near Pompeii. Once they arrive, they are soon absorbed in a quest to solve a riddle that may lead to treasure. But then tragedy strikes: Mount Vesuvius erupts and the friends must flee for their lives!
Not just a mystery - this is an absolutely thrilling action adventure that brings history to life!