Along the Mediterranean coast, the Roman empire's richest citizens are relaxing in their villas, enjoying the last days of summer. But while the gorgeous weather belies impending doom, only one man is worried. The young engineer Marcus Attilus Primus has taken charge of the Aqua Augusta, the enormous aqueduct that bring fresh water to the people around the Bay of Naples. There is a crisis on Augusta's main line - somewhere north of Pompeii, on the slope of Mount Vesuvius - and Attilus must repair the aqueduct before the reservoir runs dry. His plan is to organise an expedition in Pompeii, then head to the place where he believes the fault lies. But Pompeii proves to be a corrupt, violent town, and Attilus discovers that there are powerful forces at work - natural and otherwise - threatening to destroy him.