The imperial succession at Rome was notoriously uncertain, and where possible hereditary succession was preferred.

John Grainger's detailed study looks at aperiod of intrigue and conspiracy. He explores how, why and by whom Domitian was killed, the rule of Nerva, chosen to succeed him, and finally Nerva's own choice of successor, Trajan, who became a strong and respected emperor against the odds.

Perhaps most significantly Grainger investigates the effects of this dynastic uncertainty both inside and outside the ruling group in Rome, asking why civil war did not occur in this time of political upheaval.

The last time a dynasty had failed, in AD 68, a damaging military conflict had resulted; at the next failure in AD 192, another war broke out; by the third century civil war was institutionalized, and was one of the main reasons for the eventual downfall of the entire imperial structure. Grainger argues that though AD 96-98 stands out as the civil war that did not happen, it was a perilously close-run thing.