Marcus Attilius Primus is a young Roman aqueduct engineer from a long line of Attilia, the aqueduct engineers of the Roman Empire. In the year 79 AD, he is dispatched to the southern city of Neapolis (modern-day Naples) to work on an aqueduct that will supply the city with water. He is younger and shorter than his team. When he leads them on a pre-dawn exploratory mission, they complain about being sent on a "fool's errand" (3). The local overseer, Gavius Corax, resents receiving instructions from a younger man. Attilius decides that the best way to deal with Corax's insubordination is to "ignore him" (5). They find the cross that Attilius marked with chalk the previous day.

Attilius surveys the landscape, from the nearby dormant volcano Mount Vesuvius to the "plains of Campania" (7). The Augusta is the name of the "longest aqueduct in the world" (8) which carries water to Pompeii, Nola, Acerrae, Atella, Neapolis, Puteoli, Cumae, Baiae, and Misenum. Amid the recent drought, however, the water from Augusta has ceased to flow. Attilius has been tasked with diagnosing and repairing the problem.