The novel follows Marcus Attilius Primus, a young Roman aquarius (engineer in charge of aqueducts), who is sent to the Bay of Naples to investigate a mysterious disruption in the water supply from the Aqua Augusta. As he investigates, he uncovers signs of volcanic activity, though the danger isn’t widely understood or taken seriously.
Attilius clashes with corrupt local officials, especially Ampliatus, a former slave turned wealthy and ruthless businessman who has much to lose if the aqueduct fails. While trying to fix the aqueduct and warn the region about the impending disaster, Attilius also develops a relationship with Corelia, Ampliatus’ intelligent and strong-willed daughter.
As Vesuvius begins to erupt, chaos spreads. Attilius must fight not just the forces of nature, but also political corruption and human arrogance, to save lives and get Corelia to safety.