The medicus Ruso and his wife, Tilla, are back in the borderlands of Britannia, where he is tending the builders of Hadrian’s Great Wall. Having been forced to move off their land, the Britons are distinctly on edge and are still smarting from the failure of a recent rebellion that claimed many lives.

The tension grows when Ruso’s recently-arrived clerk goes missing, and things go from bad to worse when the young son of a local family also vanishes. As Ruso and Tilla struggle to keep the peace, an intricate and dangerous scheme emerges, and it becomes imperative that they find the boy before it’s too late.