Set in Rome and Britannia during AD 70, just after the year of the four emperors, the novel stars Marcus Didius Falco, informer and imperial agent.

The book's title refers to 200-pound lead ingot "pigs" filled with silver ore and stolen from Roman Britain,[1] which feature prominently in the plot.

Falco stumbles upon a conspiracy in the trading of silver ingots, which results in the death a young girl, Sosia Camillina.

After spending so much time together, and many arguments, misunderstandings and denials, Falco and Helena fall in love, subsequently consummating this in a horse stable, in a public garden.

As an equestrian Falco would be upper middle class and could marry Helena without bringing her or her family shame, as would with his current meagre earnings.