The Roman Mysteries: The Assassins of Rome : Book 4 by Caroline Lawrence

Jonathan goes on a secret quest to Rome, and Flavia, Nubia and Lupus set out to find him. Their dangerous mission takes them to the Golden House of Nero where a deadly assassin is rumoured to be at work - and they learn what happened to Jonathan's family during the terrible destruction of Jerusalem nine years earlier.
Binding: Paperback / softback