Britannia, AD 117: Roman centurion Flavius Ferox is trying to live a quiet life of dignified leisure, overseeing his wife's estate and doing his best to resist the urge to murder an annoying neighbour – until someone else does it for him. Dragged back into a life of violence, Ferox finds himself chasing raiders, fighting chieftains and negotiating with kings, journeying far into the north just as war breaks out.

With the new emperor, Hadrian, sending agents from Rome, the whole world seems to be changing: old friends become enemies, enemies claim they are friends, and new and deadly threats lurk in the shadows.

When, five years later, Hadrian himself comes to Britannia to inspect his great wall, a new war erupts suddenly, dividing tribes and families. Ferox is the only one who can save the emperor – but with his family, and his own life, in danger, Ferox must first decide whose side he is on...