When Ruso rejoins his unit in the remote outpost of the Roman Empire known as Britannia, he finds that all is not well with the Twentieth Legion. As they keep a suspicious eye on the barbarians to the north, the legionaries appear to have found trouble even closer to home—among the native recruits to Britannia's imperial army.

A young soldier has jumped off a roof, killing himself. Why? Mysterious injuries, and even deaths, begin to pile up in Ruso's medical ledgers, and it soon becomes clear that this suicide is not an isolated incident. Can the men really be under a curse? And what has this to do with the much-decorated Centurion Geminus?

Bound by his sense of duty and compelled by his ill-advised curiosity, Ruso begins to ask questions nobody wants to hear. Meanwhile his barbarian wife, Tilla, starts to find out some of the answers—and is marked as a security risk by the very officers Ruso is interrogating.

With Hadrian's visit looming large, the fates of the legion, Tilla, and Ruso himself hang in the balance.