Marcus used to be the slave of Linus Selius, a scientist, and his father, Tata, helped the man out with his studies. When the scientist died, Tata was sold, and Marcus' life at Festus' house in Pompeii became very difficult. Pompeii is seeing a lot of natural disturbances, and when there is a tremor in the market place that knocks an old lady down, Marcus helps her up. She warns him that dire times are coming and advises that he should "follow the hand of Mercury". When Marcus sees gladiators coming into town and recognizes his father among them, he is determined to rescue his father from certain death. The disturbances, as well as the appearance of a horse the two are able to ride, make this escape possible, but Tata feels compelled to go back to the town and let everyone know that disaster is looming and that everyone should flee. The guards don't take the slaves seriously and their freedom is again in peril. Can the two survive not only the volcano but also the evil Festus?
I'm a huge fan of this series. The books are fast paced, exciting, and impart a great deal of historical information to reluctant readers. Pompeii is covered in our seventh grade social studies curriculum.