In the summer of 83 AD Pliny the Younger receives a visit from the disguised emperor Domitian. Domitian is afraid that a previously unknown relative of Nero, supposedly the last of Julius Caesar's relatives, may be about to claim the throne. Or that Nero himself may be back from the dead. Domitian wants Pliny and his friend Tacitus to find out if any other descendants of Caesar survive, fifteen years after Nero's supposed death. Did Nero's mother, Agrippina the Younger, have any other children? What has become of her diary? Those questions seem somehow connected to the death of a mason working on Domitian's new house on the Palatine hill. When Pliny learns that the mason and his family were on the island of Pandateria while Agrippina was in exile there, he begins to make some surprising connections.