Set in Rome between July and August AD 74, the novel stars Marcus Didius Falco, informer and imperial agent.

The result is a trawl through the literary and financial worlds of Ancient Rome, as Falco delves deep into Chrysippus' personal life and business history.

Falco's investigations reveal that the deceased Chrysippus (Greek: "Golden Horse") was owner of the Golden Horse Bank, and many potential suspects are turned up, including disgruntled writers employed by Chrysippus’ scriptorium, a shipper Pisarchus who has fallen on hard times, as well as his family: Chrisyppus' widow Vibia, his ex-wife Lysa and his son Diomedes.

Meanwhile, things get worse: one of the suspected writers, Avienus, is found dead and Falco and his friend Petronius are also attacked, although they manage to survive and kill the assassin.

The novel ends on an ominous tone, with Diomedes being sentenced to a gruesome death, and Falco brooding over tensions between his family and Anacrites, who has tried to woo Maia but was spurned by her.